# Double Digit and Dollar Digit

Topics: Addition, Estimation

Materials: A die, pencil and paper, base ten blocks (optional)

Recommended Grade: 2, 3

Common Core: 2.NBT.B.5, 2.NBT.B.6
Each time the die is rolled, you can take that number of ones or tens. How close can you
get to 100 without going over?

#### Why We Love Double Digit

This simplified version of Don’t Break the Bank is quick and fun. It also provides a
strong reinforcement to students’ understanding of how to add tens and ones, and how
tw0-digit numbers behave. Perfect for a 5-minute warm-up or station.

#### The Launch

The teacher can demonstrate this game with all students playing right away
on their own paper, while the teacher rolls the dice and plays on the board.

#### The Rules

1. 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.
2. A sum of 100 exactly is a perfect game.
3. 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.
Example

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: My next roll is a 4. I’ll take 4 ones. You can take tens or ones on your own paper.
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?

#### Variations

• 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.

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