Topics: Addition, Estimation
Materials: A die, pencil and paper, base ten blocks (optional)
Recommended Grade: 2, 3
Why We Love Double Digit
- Roll 7 times. You can choose to take ones or tens for each roll. The goal is to get as close to 100 as you can without going over.
- A sum of 100 exactly is a perfect game.
- The teacher draws a T-chart as the game board, and adds in the numbers from the rolls one at a time, deciding whether each digit will be count as that many tens or ones after each roll.
Teacher: I’m going to roll 7 times. After each roll, I’m going to choose whether to count that number as a ten or a one. You do the same on your paper. We’ll see who can get closest to 100 without going over.
Teacher: My first roll is a 2. I’ll take 2 tens.
Teacher: Next roll is a 3. I think I’ll take 3 tens. Then a 5. I’ll take 5 ones. Then a 6. I’ll take 6 ones. Then a 1. I’ll take 1 ten. And then a 2. I’ll take 2 tens. Now I’ll add up my tens and ones. You do the same, and we’ll see who had the highest score.
Teacher: I have 8 tens in all, plus 15 ones. That’s the same as 9 tens and 5 ones, or 95. [Note: this is an excellent score.] Teacher: Who went over 100 and busted? [Students raise their hands.] Who got over 70 without busting? Over 80? Over 90? Did anyone beat 95?
[Teacher calls on students to explain their scores.] Student: I put the 3 and the 5 in the tens column, and all the rest of the numbers as ones. That gave me 95 too.
[optional followup question] Teacher: What’s the best score you could have gotten if you rearranged the digits now?
- Reverse Double Digit: is exactly like Double Digit, except everyone starts at 100 and subtracts ones or tens, trying to get as close to 0 as possible without going under.
- Dollar Digit: roll 7 times. For each roll, you may choose to take that many dimes, or that many pennies. The winner is the person who gets closest to making a dollar without going over $1.
- Advanced Dollar Digit (for more advanced students): roll 10 times. For each roll, you may choose to take that many pennies, nickels, dimes, or quarters. Whoever gets closest to $2 without going over wins.
- Pennies and Nickels: For younger students, play with nickels and pennies only, and try to get as close as possible to 25¢ without going over.