← Skills
MathFoundation · 8 min2.OA.B.2
Making Ten and Back
Ten is a friendly number — leaning on it makes adding and subtracting quick.
The idea
To add fast, make a ten first: for 8 + 5, take 2 from the 5 to make 10, then add the 3 left to get 13. To subtract, think of the missing part: 14 - 6 asks "6 plus what makes 14?"
Fact 1 of 10
11 + 7
Work all the way through to finish. 8 of 10 right and it’s hers.