Showing posts with label real-life problems. Show all posts
Showing posts with label real-life problems. Show all posts

Tuesday, March 16, 2010

Fathers, Sons, and Inequalities

I did a couple of days of Professional Development last week for a nearby school district. Hard work, but fun in its own way, and the teachers were very thoughtful and responsive, which was great. A few former colleagues of mine are working over there now, too, and it was wonderful to see them.

To illustrate some of my points about how children think about mathematics, I told some of my favorite stories, a few of which have appeared on this blog. But I left out this one, which took place in a kindergarten class early in my teaching career:

*****************

The little girl is almost always late being picked up. Her mother works till 3, and pickup is at 3, and the mother hasn't figured out how to be in two places at once. Technically I am supposed to send the girl to the After program if she hasn't been retrieved by 3:15, but the reality is that the After costs money, which the mom doesn't have much of. And besides, the mom is almost always there by 3:25. And anyway I'm an old softy at heart, or something.

So we have worked out a silent understanding, the girl and I. I go about my business in the classroom from 3 to the time she is picked up, tidying up and organizing the next day's work, and she sits quietly in the big rocking chair just outside the meeting corner rocking slowly back and forth, her lunch box by her side. Sometimes she looks at a book while she rocks. Other times she just rocks. It seems to be a nice decompression time for her. Once in a while we talk briefly, but she's never been much of a talker under any circumstances; so more often this is simply parallel play of a sort: the day is over, and she is in her world and I am in mine. When her mom arrives at 3:20 or 3:25, she slides out of the chair and heads for the door. "See you tomorrow," I say, but she is the strong, silent type, and so she smiles and wiggles her fingers at me in a half-mast wave, and then she is gone.

One day, though, another teacher stopped by my room at 3:20 to consult with me about something. The room was empty, of course, except for me and my late pickup, the girl in the rocking chair. I was taking clothespins off a bulletin board, if I remember correctly (and astonishingly, I think I do), and she was rocking, of course, the chair creaking as she meditatively swung back and forth.

The consultation finished, the teacher noticed that I was wearing a sweater (this was in the days when I still occasionally wore long sleeves). "Nice sweater," she said approvingly. "It looks handmade. Did someone make it for you?"

"Um," I said. "Well, sort of. My sister made it, knitted it for my father. But it turned out to be too small for him, so he passed it along to me."

The teacher nodded. "It seems to fit you just fine," she said, "and it's certainly striking," and with that she ducked back out of the room, and I returned to my clothespins to the accompaniment of the familiar, faint creak of the rocking chair--

When, quite suddenly and unexpectedly, the girl spoke up. "Your daddy is older than you are," she said.

I had almost forgotten she was in the room. Turning, I saw that she had a satisfied smile on her face. "Your daddy is older than you," she repeated, just in case I hadn't heard it the first time.

"Yes," I agreed. "That's right." Well, of course it was right. But I couldn't resist finding out the details of her thinking process. "What makes you say so?" I asked.

"The sweater was too small for your dad," she said proudly, her chair busily creaking as always, "but it fit YOU. So you are smaller than your dad. And if you're smaller than he is, then you must be younger, because people who are young are small." Creak, creak went the chair as she rocked harder and more enthusiastically. "So that means your dad has to be older than you."

What could I do but congratulate her on her remarkable reasoning ability? And it WAS impressive, even if entirely unnecessary, and this tiny little girl, not yet even six years old and still unwise in the ways of the world, deserved all the praise she could get. "You're absolutely right," I said, nodding my head slowly. "My dad IS older than me. You did a great job of figuring it out."

"Thanks," she said, taking the compliment as her due, and just then her mother walked in the door, and the girl slid off the rocker, exactly as she had done a few dozen times before, and she wiggled her fingers at me with a larger-than-usual smile. And though it's been probably twenty-five years since that incident, and though I lost track of that little girl long ago, I can still hear the creak of the rocking chair and see the self-satisfied grin on her face as she explained her impeccable logic...

Ah, memory. It's a funny thing.

Monday, February 15, 2010

Obi-Wan, Mini Hot Dogs, and the Ninety-Dollar Jar of Olives

Hungry? You’ve come to the right place. Some of our second graders have been spending a few of their math periods lately planning menus for a special dinner. If they have leftovers (and judging from the amount of food some of them are planning to buy they’ll have lots), I’m sure they’d love to have you drop by.

Each of the children was instructed first to draw up a guest list consisting of seven fictional characters they’d like to get to know better. Their lists skewed heavily toward fantasy fiction: Lord of the Rings, Harry Potter, the Star Wars crowd. Obi-Wan Kenobi, in particular, will be kept busy nearly every evening for a week with invitations to these foodfests.



Next, they sketched out seating arrangements. One child set up four tables of two people each. Another planned for two tables, each seating four. Someone else constructed an octagon. (Eight people? Yes--seven guests and a host.) Then they planned a menu. “Not just desserts,” I cautioned them when it seemed clear that this was the way the wind was blowing. “A main course, or even two, so people can have a choice. An appetizer, perhaps. Soup, salad. Fruits and vegetables. Drinks.” “Oh, okay,” they said, and proceeded to put together menus that were...well, idiosyncratic, or what else would you call it when red snapper and turkey are served side by side?

Now came the most mathematical part: shopping. We did this in the comfort of our own classroom, using grocery ads from newspaper inserts as well as the circulars that arrived in my mailbox over time. I gave the children record sheets as well. “Find the items you want to buy,” I told them. “Record what the item is and how much it costs to buy just one. Then decide how many of the item you need. What will the total cost be? Figure that out and record it here in this column; then round that to the nearest whole dollar to make estimating the grand total easier.”

The children fell eagerly to work. “Mini hot dogs, mini hot dogs,” one boy repeated over and over, scanning the ads in vain for his favorite entrĂ©e. “Pizza!” crowed a classmate, jabbing a pencil at a listing in the frozen foods section of one advertising supplement. “Pizza?” asked a classmate. “Hey, I need that too!”



The kids needed help deciphering some of the prices: supermarkets, we learned, don’t often write prices the way teachers say you should. Instead of $1.59, for instance, they often write a big 1 followed by a smaller 59 and no decimal point or dollar sign at all: “Looks like a hundred and fifty-nine dollars,” one child said disapprovingly. “5 for $2” was confusing enough, but “4/3” to mean “you can get four for three dollars” was enough to make strong second graders cry. (Well, not literally. They were good sports about it and chalked it up as yet another example of the weirdness of adults.)

Determining how many of each item they needed was again idiosyncratic. One child decided that each person would probably eat 5 cookies, no, make that 6, so he settled on 48 as the number to buy. Somebody else, less generous or perhaps expecting that everyone would be full when dessert came around, decided to purchase just one small apple pie for the table. Did you need one carton of orange juice, or were you better off with 10? Different kids answered similar questions in wildly different ways.



Determining the cost of n cartons of orange juice, when n was more than 1, was often tricky as well. Some of these hosts have a beginning knowledge of multiplication, which they used to good effect. “Each cookie costs ten cents,” mused our 48-cookie-buying friend from before, “so 48 of them would cost, um, $4.80.” One child bought two jugs of milk at $2.99 apiece, set up the costs in columns, and laboriously regrouped to arrive at the total, $5.98; another, trying to determine the cost of two $4.98 items, rounded up to $5 for each, added the estimates to get to $10, and finally subtracted the extra four cents for a total of $9.96. We shared strategies and tried out newer, more efficient ones.




What about items that appeared on menus but were nowhere to be found in the ads? I hear you ask. Surely there were some of those. There were indeed, the aforementioned red snapper and mini hot dogs were among them. “Not a problem,” I said. “You have an idea of what similar things cost. Estimate the price. Just put a circle around the price on your record sheet to indicate that it’s an estimate.” Some estimates were IMHO pretty good. Others were...well, one cent for salad dressing was perhaps overly optimistic, and over $100 for a few other items seemed a tad excessive, but hey, who am I to complain?



Once the estimates were done, it was time to find a grand total. Making an estimate (using the rounded-to-the-nearest-dollar figures on the shopping list) was a job for mental arithmetic. Finding the actual total was a job for a calculator. Children compared the answers to make sure their totals were reasonable, then looked again at the total bill.

At first each was flabbergasted by the high cost of groceries (especially given the $90 jar of olives one of them purchased--an estimate, natch), but after a moment flabbergast vanished to be replaced by pride. Yes, indeed, they seemed to be saying, a meal that costs over $500 must certainly be something special. Now if only they’d found more expensive broccoli and purchased twelve loaves of bread instead of just two--

So the menus are done, the shopping lists are ready to go, and all that remains is to check on the availability of the guests. Anyone know if Dumbledore is free the evening of the 23rd? The invitation says six pm sharp, but he can arrive at seven if he doesn’t mind missing the goldfish and gummiworms being served as appetizers...

Friday, February 5, 2010

Cheerful Charlie and the Cupcakes

My good friend Cheerful Charlie, I told the third and fourth graders, was having a party, at which he planned to serve cupcakes. One hundred cupcakes, to be precise. I'm not sure who-all is on his guest list (other than me, of course), but he's either inviting a lot of people, or a few big eaters, or else he just wants a lot of leftovers.

Cheerful had (wisely) decided not to make these cupcakes from scratch (his measuring skills aren't what you would call real accurate), but was having some trouble determining which store he should go to. He had three choices, I explained, and he wanted to spend as little money as he could and get as good a deal as possible, and if the students could advise him that'd be great.

So, there was Cupcakes R Us, I told the kids, which sold baskets of 50 cupcakes at a shot, and each basket cost $40 but he also had to pay a fee of $5 to park.

And there was Cupcake Depot, where cupcakes were $9 per bag for a bag of 10, plus which Cheerful had a coupon for $5 off his total purchase.

And there was Cupcake's Discount Warehouse...

Look at all the information, I told them, and do some calculations if you need to, and decide if there are other considerations Cheerful should be thinking about, and then write Cheerful a letter suggesting what he ought to do. The students could turn in a handwritten letter which we'd forward on to Mr. Charlie, I explained, or they could email him directly at cheerful.charlie@yahoo.com, an account which he checks but not as regularly as he should because he often forgets or mistypes the password.

For some students, the assignment was just a relatively straightforward problem in arithmetic. You determine how many bags, boxes, or baskets of cupcakes Cheerful needs to buy at each store so he has 100 cupcakes in all; you multiply that number by the cost per box/bag/bucket/basket; you add the parking fee or membership fee, you subtract the coupon...and if you've done it right, you inform Cheerful that the cost at all three stores is the same, eighty-five bucks, and he can go wherever he likes and it doesn't make any difference. And this is a fine way of looking at it.

But what makes the problem interesting is the real-world nature of it. Sure, price is important. But is the lowest price always the best deal? I remember when my wife and I discovered WHY generic spaghetti sauce was so cheap (hint: it contained mostly water)... So the question becomes, what other things should Cheerful be taking into account?

Well, a lot of kids came up with lots of ideas.

"You should go to Cupcake's Discount Warehouse," one student wrote. The membership fee of $5 was annoying, she pointed out, "but if you have to go back again you will have your membership card so it'll be cheaper."

"Maybe you can walk to Cupcakes R Us," said somebody else. "Or ride a bike. Then you might not have to pay to park." (Note the "might." Hedging your bets, we call it.)

"It depends," wrote another student. "How far away are the stores?" A good question. If the nearest Cupcakes R Us outlet is in Albany, Scranton, or Paramus, it isn't worth the time and the gas to get there.

"You should ask them each for a free sample," suggested one optimist. "If you say you'll buy a lot they'll probably let you have one. Buy the one that tastes best." Not much point in saving five dollars if the cheaper cupcakes tasted like sawdust or carbon paper. --Or were made primarily of water, like the generic spaghetti sauce referred to above.

"Buy them in bags of 10," someone else advised. "The prices are all the same but if you need more then you only have to buy 10 more, not 20 or 25 or 50, and that will save you money."

And another student went right to the heart of the matter: Measure the cupcakes. "Buy the ones that are biggest," he suggested.

Unfortunately, Cheerful (who likes things simple) is still uncertain what to do: he's definitely bummed at the prospect of needing to find more information. We'll keep you posted. In the meantime, it was nice to see how many students recognized that there might be other considerations besides the cost of the cupcakes. We like to remind kids that math is about real-world situations, and in particular we like to point out that answers may not be as cut and dried as the textbooks sometimes suggest they are. This was a good example of both--and a good example of how a little knowledge can be a dangerous thing.

(Though regarding "other considerations," you CAN have too much of a good thing: see one of my favorite cartoons of all time, http://xkcd.com/309/. --Cut and paste the URL into your browser window if the link doesn't work for you. The two folks on the extreme right? That would be me and my wife...)

Sunday, November 1, 2009

Corn, Revisited

I promised to write more about the corn project (see entry of October 13). Picking up the story from there:

Once all the students had the complete and accurate number of kernels, we assembled in the Chapman Room. "Who thinks they have the MOST kernels of anyone in all three classes?" I asked. Several people were pretty sure the honor was theirs, but one young man from Jan's class took the prize: he had 644 kernels on his ear of corn, a full 43 more than the next runner-up.

"Okay, how about the LEAST?" We had a few who coulda been contendahs, but again one student won out--another of Jan's students, down at 289.

All right. We had the greatest and the least values. One way of describing a set of numbers, I explained, is to find the range: the distance between the least and the greatest. (This tells you roughly what kind of a spread you have in the data: are the numbers generally pretty far apart, or are they mostly close together?) As a group, we estimated the difference, then subtracted to find out. "Close together, or far apart?" I asked when we had our result.

"FAR APART," chorused 48 voices.

How right they were. The range was--quite large. Taken together, the two lowest figures were less than the highest. There's plenty of variation among ears of corn, evidently.

Next we turned our attention to the median, or the center value when the numbers were all ordered. We had the students sit in a line--well, technically a curve--arranged from 289 up to 644. When everyone was in order I had them all stand and look around. "Where do you think the median value is?" I asked. "Point to the person who you think had the median amount of corn kernels."

Fingers waved toward the middle of the line. Most people in the middle of the line pointed to themselves. To find out the real answer, we started at the outside of the line and had students sit down two by two: 644 matched with 289, 601 matched with 293, and so on. Like a very slow row of falling dominoes, or perhaps like spectators doing the wave at a baseball stadium, they sat down, or fell down, depending on their level of coordination and their penchant for dramatics. Little by little, the number of children standing diminished. The 500s disappeared altogether, so did the 300s. The upper 400s took their seats. People began revising their predictions.

Before long, we were down to two students. One had amassed a total of 408 kernels. The other had--412. There was an even number of people. The answer, someone realized, was to split the difference, and that's exactly what we did. The median was 410. If you wanted to choose one number to stand for all the numbers in the group, you could do a lot worse than choose 410.

(The picture below shows the Final Two. Everyone else has been eliminated from contention as the Merry Median of the Corn Kernels. Thanks to Jan for the photo.)



One more project remained. You've heard of the Living Flag? Well, this was to be a Living Histogram. (A histogram has nothing to do with allergies--it's a bar graph in which the bars stand for a range of numbers rather than a single figure or response.) We had the students divide themselves into groups, according to the number of kernels: up to 299 over here, 300-349 over there, 350 to 400 in that corner. Then we called the groups over one by one and had group members sit in a line, creating eight lines of varying lengths in all. "What do you notice?" I asked, and they noticed quite a lot. The longest line was in the middle, they explained, the shortest lines on the outside. It was like stairs, someone said; it was like a roller coaster, said someone else. They were quite right, too. It was about the normal-est curve I'd encountered in the last few months--the nice bell shape you read about.

(Here are the lines. You might recognize the two almost-median-winners, smack dab in the center of the longest line there in the middle of the photo. See how neatly all these things work out?)



So, a nice way to spend a misty, mathy morning. The kids enjoyed getting their minds around the concept of range and median--and did it very well, I might add. They were surprised to see how big the range actually was, and they very much liked using their own bodies to locate the median. And while some of the players were beginning to get a bit restless toward the end, they kept their sense of curiosity about the graph and loved the idea of constructing it themselves. We'll continue to explore range and median--and who knows, we may get back out to the Chapman Room with a different set of data someday!

Tuesday, October 13, 2009

Corn

How many kernels on an ear of corn? we asked the third and fourth graders the other day. They've been studying the Mayan people, who called themselves "People of the Corn," so it was a worthwhile question.

We started by having students find approximations; as you should know by now if you've been reading this blog, us Math Guys consider this a very important step. We asked students to choose a round number (a number that is a multiple of 10); the point, after all, wasn't to guess the exact number, but to use a number that makes some sense and is relatively easy to work with. You can always revise your estimate later, we assured them.



What is the estimate based on? Well, we gave them each an ear of dried corn to eyeball. Some did some quick-n-dirty calculations, fourth graders in particular. (Yes, we asked them to justify their reasoning. Some of them HATE this, but it's oh-so-good for them.)

"About 20 in each row," wrote one student. "Maybe 10 rows. 10 x 20 = 200. I estimate 200 kernels in all."

"I think there are 20 rows and 30 in each row," reported someone else, "but that might not be enough so I added a few more. I say 640."

"I think 260," wrote a third grader, who would have been happy to leave it at that, but who added, under duress from a teacher, "because it looks right. And because it's a good number." We might call this strategy "Pick-a-large-number, any-large-number, and-assign-it-great-virtue-so-critics-will-be-cowed."



The next step: Count the kernels! The classroom teachers had prepared egg cartons with ten cuplets (better them than me). Kids used their fingernails to push the kernels off the cob (great fun). Then they distributed the kernels 5 or 10 at a time into the cups, making groups of 50 or 100. Record the number, dump out the kernels, lather, rinse, repeat.



At some point along the way several students noticed that their estimates weren't looking as accurate as they had back before counting had begun. This was especially true for those whose initial strategy had been "Pick-a-large-number, any-large-number &c," but other more careful estimators ran into this difficulty too. No problem! we said. Just revise your estimate, record it--oh, and explain why you wanted to change your original prediction. (My favorite: "Because I passed my first estimate a long time ago.") You will no doubt be shocked to learn that the second set of estimates were considerably closer than the first.

Eventually, all corn kernels were off the cobs and had traveled through the eggcups and into plastic bowls or paper bags (except for a few strays which had found their way onto the floor), and everyone had an exact answer. Some were surprised to see how many there were. Others found the results unsurprising in the extreme, or claimed they did: "I knew it," crowed one boy whose answer was not, perhaps, as close as he thought.

As students finished, they compared their totals with friends and thought about questions such as Why aren't all the totals the same?, What could you do to get a better estimate next time? ("Nothing," said the young man quoted above), and About how many kernels do you think there might be in the whole class?

So, three-digit numbers, ordering, estimating, grouping by tens, fives, 50s, and 100s, and explaining reasoning. Plus, a fun project (there's something truly satisfying about flicking those kernels off the cob, and something even more satisfying about running your fingers through a nice big tub full of everyone's kernels), and one that relates to science and social studies. A worthwhile math period indeed. Next up: data analysis with these results. On Thursday we'll be in the Chapman Room calculating the median and range of the data and forming a Living Histogram. Pictures to follow, assuming my camera behaves itself...

Wednesday, September 30, 2009

Pizza!

As many of you know, the third and fourth grade classes order pizza each Friday. Children throughout the lower school put in their order; runners from the 3-4s pick up the orders and the money, determine the number of pizzas to buy, and hand-deliver it when it arrives.

Pizza is a major undertaking. There are times when we teachers wonder whether it is all worthwhile, especially when we discover that one class is short $15 or that a dozen or so children neglected to sign up until the pizza, you know, arrived... BUT we continue to do it because pizza a) tastes good, b) is convenient for parents, and c) IS A GREAT TOOL FOR PRACTICING MATH SKILLS. Of the three, c) is by far the most important in my book, though your mileage may vary.

How does pizza relate to mathematics? Glad you asked. Let us count the ways...

1. Pizza order takers get good practice in counting money and determining if it matches the number of slices ordered (hint: it does only about half the time).
2. Students get practice in giving and making change.
3. Students round the number of slices ordered per class to the nearest multiple of 10 to make estimation easier.
4. Kids practice addition skills by calculating the total number of slices ordered.
5. We look at number patterns. Hmmm: when a class orders 14 slices at $1.50 per slice, we get $21. Interestingly enough, 14 plus half-of-14 equals 21--the same number, only in regular numbers rather than in money. Now why would that be?
6. Especially later in the year, we use pizza as a real-life example of multiplication--if there are 8 slices per pizza, how many slices in 5 pizzas? In 7 pizzas? In 13 pizzas?
7. Kids calculate the profit for each week's worth of pizza: if we charge a dollar-fifty per slice after buying it for [sorry, trade secrets removed--suffice it to say "less"] per slice, how much money is left over? What operation can we use to calculate it?

And there are many other ways we mathicize pizza, especially this year, but I've been typing all day and my fingers are about to fall off. So you'll have to wait for another post. Sorry! In the meantime, how about some pictures? ...Yes, yes, the very thing!

Some of the proceeds, up close and personal:



This young man is clearly enjoying himself.
Think Scrooge McDuck.



Doublechecking that the amount of money from one of the 1-2 classes actually matches the number of slices ordered:



One of the "Grand Totalers," making bundles of ten for easier counting:



And at last, the fruits of our labors--or seven eighths of them at least (did I mention that pizza and FRACTIONS go well together? No? Consider it mentioned...):

Sunday, May 3, 2009

George's Excellent Adventure

Sometimes the best lessons are the ones you don't plan.

Friday morning, Ellen poked her head into the office as I was preparing for a fraction lesson with the 1-2s. "Elizabeth found a Where's George dollar in her lunch money," she said. "Okay if we take a few minutes to enter it at the beginning of math time today?"

Where's George, I should explain, is a lovely internet project that tracks paper money as it moves across the country (www.wheresgeorge.com). Since the 3-4 classes handle lots of money in their capacity as Pizza People, they occasionally run into Where's George bills, which are recognizable by special markings. We log onto the site, enter the bill's serial number, note our location, and press Enter. If the sound on my laptop is turned on, we'll then hear a cash register noise and the bill's previous location(s) will appear. Most of the bills we've found thus far have come from nearby places such as Pennsylvania and Massachusetts, Brooklyn and Kingston, but we've had bills from Missouri, Tennessee, and Texas as well. It's fun, and suspenseful, and teaches a bit about geography--and you never know when someone will find "our" bill and put it in again.

When we entered Elizabeth's bill, the screen showed that the bill was now 1128 miles from its original location. I had a sudden brainstorm. Instead of scrolling down and telling the class where the bill had come from, I'd have them narrow the possibilities by using math--specifically, their measuring and estimation skills. They'd been working on maps all year long, after all, filling in states that Cheerful Charlie had visited in his round-the-US tour. Ellen got one of the students' maps, and we hung it up. We determined that 1128 was very close to 1100, in double-round numbers, and at 200 miles to the inch, the class quickly calculated that the starting point was about 5.5 inches away from us.

It was clear to most of the students that the possibilities would form the arc of a circle, and so we did a little measuring. We ended up with a curve beginning at the western end of Michigan's Upper Peninsula and then zagging through Wisconsin, Minnesota, Iowa, Missouri, Arkansas, and Mississippi--all of them marked on the students' maps--before catching a piece of south-central Florida and disappearing over the Atlantic Ocean. "Why can't the bill have started here?" I asked, indicating where the arc crossed the Gulf of Mexico. That was obvious. "It's too wet for money in the ocean," a third grader answered (unless, he added, there were islands he "didn't know about"). As for why we didn't go north of Michigan, that was obvious too: Canada has its own money.

I scrolled down on the webpage and revealed the answer: the bill had originated in Florida. ("I knew it!" half the class exclaimed.) I named the town, which I'd never heard of. But Ellen had: her brother lived there. She asked if there was any way to find out who started the bill on its travels. Well, yes, there was; I clicked on the profile button and found a first name, Bob.

It wasn't Ellen's brother. But that was all right. Bob had provided us with a nice map of the US, each state filled in with one of six colors. Now I had my second brainstorm. We'd done a little real-life estimating and measuring with scale; it was time for some real-world data analysis.

"What do you think this map shows?" I asked, turning the computer so the students could see. Temperatures, guessed one boy. Good thought, but no. How many people live in each state? asked a girl. Close, I said. Think about what website this is, Ellen suggested, and suddenly hands were flying up all over the meeting area. Bob, they realized, had marked dozens and dozens of bills and sent them into the wild. The colors showed how many of those bills had turned up in each state.


[Here is Bob's Hit Map, by the way:]

Right on the money! (So to speak.) The only question now was which colors stood for the most bills and which for the fewest. To help, I had them identify a few key states on Bob's map, and then I gave them a little extra information. California, I explained, had the most people of any state. Texas, New York, and Florida were next. Wyoming took up a lot of space, but it had fewer people than any other state.

Working as a group, the class swiftly came up with a sensible schematic for the colors. Red, the color of Florida, California, and New York, would be the most. Bright green, it seemed apparent, would be next, judging from what the children knew of population and distance, and so on, down to lowly Wyoming, the only state that was colored gray.

The guesses were in. It was now time for the Great Unveiling. I had everyone's full attention: they were deeply invested in the outcome by now. And the results were entirely satisfactory. The class had four out of six colors right; the only error had been reversing the orderof the fourth- and fifth-most colors.

Not bad, not bad at all, I told them, and we moved on to the regularly scheduled lesson on division.