# Difference from 100 Math Game

Making 100 is nearly as important a skill as making 10, and the two skills are clearly related. This Difference from 100 math game will have your students composing 100 in no time!

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Think, for example, of finding the difference between 53 and 100. Mentally, you probably look at the ones place, see a 3 and know that you need 7 to make a 10, so in trying to make 100, you’re actually relying on what you know about making 10. The big mistake students make (and adults, too!), of course, is to think that the difference between 53 and 100 is 57, not 47.

A 100 chart is a great tool for composing 100. It also helps students understand how to find the difference between two numbers by counting up or by removing chunks to subtract.

The game is for two players. For each pair, you’ll need two standard number cubes and a 100 chart, which you can download at the bottom of this post. You might also provide players with transparent discs, which work well for counting on the 100 chart. The goal of the game is to have the smallest difference for each round. On their turn, a player rolls the two dice and creates a 2-digit number. So if the player rolled a 3 and a 5, they could make 35 or 53. Which should they choose if they want the *smallest difference*? Let them figure that out!

The player then finds the difference between their number and 100. In our example, the difference between 53 and 100 is 47. Students should be allowed to use the strategy of their choosing. To emphasize the connection between addition and subtraction, the recording sheet asks them to write both the addition and subtraction equation for finding the difference.

You can grab the 100 chart, instructions, and recording sheet using this link.

Great game for an important skill!

Tara

The Math Maniac