Grade 2 Mental Math: Friendly Numbers

Worked examples

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

1. Example 1

   69 + 29 = ?

   1. Break apart both numbers by place value.
   2. 69 = 60 + 9
   3. 29 = 20 + 9
   4. Add the tens: 60 + 20 = 80
   5. Add the ones: 9 + 9 = 18
   6. 18 ones = 1 ten and 8 ones (regrouping)
   7. Combine: 80 + 18 = 98

   Answer: 98

2. Example 2

   77 + 12 = ?

   1. Break apart both numbers by place value.
   2. 77 = 70 + 7
   3. 12 = 10 + 2
   4. Add the tens: 70 + 10 = 80
   5. Add the ones: 7 + 2 = 9
   6. Combine: 80 + 9 = 89

   Answer: 89

3. Example 3

   68 + 17 = ?

   1. Break apart both numbers by place value.
   2. 68 = 60 + 8
   3. 17 = 10 + 7
   4. Add the tens: 60 + 10 = 70
   5. Add the ones: 8 + 7 = 15
   6. 15 ones = 1 ten and 5 ones (regrouping)
   7. Combine: 70 + 15 = 85

   Answer: 85