Why does my child think sides of 3 and 4 make a hypotenuse of 7?
Your child adds the sides instead of their squares, such as shorter sides of 3 and 4 giving a hypotenuse of 7 instead of 5.
Why children do it
Adding the two sides is a natural first guess. But the hypotenuse is shorter than the other two together: it's the straight way across. Pythagoras adds the squares: 3² + 4² = 9 + 16 = 25, and the square root of 25 is 5.
How to help at home
Ask them to draw squares on each side: the two small squares' areas add up to the big one.
The right way
Find the length of the hypotenuse, x.
- 3² + 4² = 25Square the two shorter sides and add.
- 5Take the square root: √25 = 5.
Find out where your child is
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