Square numbers ending in 5
Multiply the first digit by the next number up, then write 25. 65² = 42 then 25 = 4225.
How long?
Type the answer. Correct answers move on by themselves. Press Enter to skip a wrong one.
How the trick works
- Take the digits before the 5.
- Multiply that number by the next number up.
- Write 25 at the end.
Worked examples
35²: take 3 and multiply it by the next number: 3 × 4 = 12.
Write 25 after it: 1225.
65²: take 6 and multiply it by the next number: 6 × 7 = 42.
Write 25 after it: 4225.
95²: take 9 and multiply it by the next number: 9 × 10 = 90.
Write 25 after it: 9025.
Practise it
Take the 1 minute drill above a few times. When you can do most of them without slowing down, try level 5, which mixes this trick with others.