Kung Fu Math · kungfumath.app
Mental arithmetic shortcuts
Choose friendly numbers, calculate one step at a time and estimate the result before checking your exact answer.
Divide in chunks
- 192 ÷ 16 = 160 ÷ 16 + 32 ÷ 16 = 10 + 2 = 12
- 252 ÷ 12 = 240 ÷ 12 + 12 ÷ 12 = 21
- Divide by 5: double, then divide by 10.
- 135 ÷ 5 = 270 ÷ 10 = 27
Add & subtract friendly numbers
- 738 + 123 = 738 + 100 + 20 + 3 = 861
- 298 + 47 = 300 + 47 − 2 = 345
- 503 − 198 = 503 − 200 + 2 = 305
- 12.4 − 7.2 = 5.2; align the decimal places.
Multiply without overload
- 8 × 36 = 8 × 30 + 8 × 6 = 288
- 16 × 25 = 4 × 100 = 400
- 48 × 5 = 240; halve 48 × 10.
- 12 × 8 − 12 ÷ 4 = 96 − 3 = 93
- 12% of 20 + 12 = 2.4 + 12 = 14.4
- Calculate multiplication/division before addition/subtraction.
Kung Fu Math · mental-arithmetic · kungfumath.app/cheat-sheets