Choice 1. He did not square 40, he just multiplied by 2.
Step-by-step explanation:
Step 1:
According to the Pythagorean theorem, the square of the hypotenuse is equal to the sum of the squares of the other two sides.
The hypotenuse measures c cm while the other sides are 40 cm and 9 cm each.
Step 2:
According to the Pythagorean theorem,
![9^{2} +40^{2} = c^{2}.](https://tex.z-dn.net/?f=9%5E%7B2%7D%20%2B40%5E%7B2%7D%20%3D%20c%5E%7B2%7D.)
![81 + 1600 = c^{2} .](https://tex.z-dn.net/?f=81%20%2B%201600%20%3D%20c%5E%7B2%7D%20.)
![1681 = c^{2} .](https://tex.z-dn.net/?f=1681%20%3D%20c%5E%7B2%7D%20.)
![\sqrt{1681} = c.](https://tex.z-dn.net/?f=%5Csqrt%7B1681%7D%20%3D%20c.)
This is the correct solution to the given problem. Hans did not square 40, he just multiplied by 2. Which is the first option.