This great math practice game was created by Becky Kinney of moonlightmultimedia.org
Our thanks to her for letting us use it on our site. All Rights Reserved - MoonlightMultimedia
Complements of 10
Complements are numbers that go together in some way.
In Geometry, the word complement is used to describe two angles that add up to exactly 90 degrees. For example, 70 degrees is the complement of 20 degrees.
In place value, the number 90 has no special significance, but the number 10 does!
When students know the complements of 10 better than any of their other sums, they are more likely to choose addition strategies that reinforce their understanding of place value. For example, when computing 7 + 6, a student might think,
"7 + 6. Well, 7 is 3 away from 10 so... If I take the 7, plus 3 from the 6 I get 1 ten. 3 from 6 is 3. 1 ten and 3 ones is 13".
See how fast you can pair up 10 complements of 10.
