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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Lesson Notes