Why does my child get a shorter side longer than the hypotenuse?
Your child adds the squares to find a shorter side, such as √(13² + 5²) ≈ 13.9 instead of √(13² − 5²) = 12.
Why children do it
Children often learn Pythagoras as square, add, square root, and use it for every side. That finds the hypotenuse. For a shorter side, take the squares away instead: with a hypotenuse of 13 and a side of 5, 13² − 5² = 144, so the side is 12. A shorter side always comes out less than the hypotenuse.
How to help at home
Ask them which side is longest: a shorter side must come out less than the hypotenuse.
The right way
Find the length of the side x, to 1 decimal place.
- 10² − 7² = 51The hypotenuse is 10, so subtract.
- 7.1√51 = 7.14..., which is 7.1 to 1 decimal place.
Find out where your child is
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