Grade 2 Mental Math: Break Apart Strategy

Worked examples

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

1. Example 1

   66 + 27 = ?

   1. Break apart both numbers by place value.
   2. 66 = 60 + 6
   3. 27 = 20 + 7
   4. Add the tens: 60 + 20 = 80
   5. Add the ones: 6 + 7 = 13
   6. 13 ones = 1 ten and 3 ones (regrouping)
   7. Combine: 80 + 13 = 93

   Answer: 93

2. Example 2

   45 + 17 = ?

   1. Break apart both numbers by place value.
   2. 45 = 40 + 5
   3. 17 = 10 + 7
   4. Add the tens: 40 + 10 = 50
   5. Add the ones: 5 + 7 = 12
   6. 12 ones = 1 ten and 2 ones (regrouping)
   7. Combine: 50 + 12 = 62

   Answer: 62

3. Example 3

   69 + 21 = ?

   1. Break apart both numbers by place value.
   2. 69 = 60 + 9
   3. 21 = 20 + 1
   4. Add the tens: 60 + 20 = 80
   5. Add the ones: 9 + 1 = 10
   6. 10 ones = 1 ten and 0 ones (regrouping)
   7. Combine: 80 + 10 = 90

   Answer: 90