Sure! Here’s a math test on the Pythagorean theorem for a 12-year-old:

1. Find the missing side length in a right triangle with legs measuring 5 cm and 12 cm.
2. Determine whether the triangle with side lengths 9 cm, 12 cm, and 15 cm is a right triangle.
3. A ladder is leaning against a wall. The base of the ladder is 8 ft away from the wall, and the ladder is 10 ft long. How far up the wall does the ladder reach?
4. The hypotenuse of a right triangle measures 13 cm, and one of the legs measures 5 cm. What is the length of the other leg?
5. A right triangle has a hypotenuse measuring 17 cm and one leg measuring 8 cm. What is the length of the other leg?
6. A right triangle has a hypotenuse measuring 10 cm and one leg measuring 6 cm. What is the length of the other leg?
7. Determine whether the triangle with side lengths 7 cm, 24 cm, and 25 cm is a right triangle.
8. Find the missing side length in a right triangle with legs measuring 3 m and 4 m.
9. A right triangle has a hypotenuse measuring 26 cm and one leg measuring 10 cm. What is the length of the other leg?
10. A right triangle has a hypotenuse measuring 15 cm and one leg measuring 9 cm. What is the length of the other leg?

Remember to use the Pythagorean theorem (a^2 + b^2 = c^2) to solve these problems. Good luck!