Grade 3 Mental Math: Mixed Mental Math

Worked examples

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

1. Example 1

   30 × 2 = ?

   1. 30 is 3 tens, so 30 × 2 is 3 × 2 = 6 tens.
   2. 6 tens = 60, so 30 × 2 = 60

   Answer: 60

2. Example 2

   68 + 54 = ?

   1. Break apart both numbers by place value.
   2. 68 = 60 + 8
   3. 54 = 50 + 4
   4. Add the tens: 60 + 50 = 110
   5. Add the ones: 8 + 4 = 12
   6. 12 ones = 1 ten and 2 ones (regrouping)
   7. Combine: 110 + 12 = 122

   Answer: 122

3. Example 3

   5 × 7 × 2 = ?

   1. Look for friendly numbers: 5 and 2 make a round number. Change the order to put them together: 5 × 2 × 7.
   2. Multiply: 5 × 2 = 10, so now you have 10 × 7.
   3. Multiply: 10 × 7 = 70.
   4. So 5 × 7 × 2 = 70.

   Answer: 70