Divide by 5
Double it, then divide by 10. 85 ÷ 5 = 170 ÷ 10 = 17.
How long?
Type the answer. Correct answers move on by themselves. Press Enter to skip a wrong one.
How the trick works
- Double the number.
- Divide by 10 by removing a zero or moving the decimal point.
Worked examples
85 ÷ 5: double it first, 85 × 2 = 170.
Then divide by 10: 170 ÷ 10 = 17.
140 ÷ 5: double it first, 140 × 2 = 280.
Then divide by 10: 280 ÷ 10 = 28.
365 ÷ 5: double it first, 365 × 2 = 730.
Then divide by 10: 730 ÷ 10 = 73.
Practise it
Take the 1 minute drill above a few times. When you can do most of them without slowing down, try level 3, which mixes this trick with others.