Grade 2 Mental Math: Compensation Strategy

Worked examples

Real problems from the practice worksheets, solved one step at a time.

1. Example 1

   51 + 17 = ?

   1. Break apart both numbers by place value.
   2. 51 = 50 + 1
   3. 17 = 10 + 7
   4. Add the tens: 50 + 10 = 60
   5. Add the ones: 1 + 7 = 8
   6. Combine: 60 + 8 = 68

   Answer: 68

2. Example 2

   78 + 18 = ?

   1. Break apart both numbers by place value.
   2. 78 = 70 + 8
   3. 18 = 10 + 8
   4. Add the tens: 70 + 10 = 80
   5. Add the ones: 8 + 8 = 16
   6. 16 ones = 1 ten and 6 ones (regrouping)
   7. Combine: 80 + 16 = 96

   Answer: 96

3. Example 3

   59 + 9 = ?

   1. Break apart both numbers by place value.
   2. 59 = 50 + 9
   3. 9 = 0 + 9
   4. Add the tens: 50 + 0 = 50
   5. Add the ones: 9 + 9 = 18
   6. 18 ones = 1 ten and 8 ones (regrouping)
   7. Combine: 50 + 18 = 68

   Answer: 68