Adding and subtracting within 100: Grade 2 mental math strategies
Five mental math strategies Grade 2 children use to add and subtract two-digit numbers, with examples for each.
By the end of Grade 2, children are expected to add and subtract within 100 fluently using strategies based on place value. Here are the strategies they are likely to meet at school.
1. Split into tens and ones
34 + 25: add the tens (30 + 20 = 50), add the ones (4 + 5 = 9), then combine: 59.
2. Jump on a number line
47 + 26: start at 47, jump 20 to 67, then jump 6 to 73. For subtraction, jump backwards.
3. Make a ten
38 + 7: take 2 from the 7 to make 40, then add the remaining 5: 45.
4. Count up to subtract
62 − 58: instead of taking away, count up from 58 to 62. It is 4. This works well when the numbers are close together.
5. Use a nearby friendly number
45 + 19: add 20 instead (65), then take away 1: 64.
Which strategy is best?
There is no single best strategy. Good mental maths means choosing a method that suits the numbers. Ask your child "how did you work it out?" and let them show you.