One square grid is formed of 400 squares. Another square grid is formed of 256 squares. If the two grids join with a third at their vertices to form a right triangle, how many total squares could their be in the third grid?

A. 4

B. 12

C. 36

D. 144

One square grid has an area of 400.

Another square grid has an area of 256.

The area of the third grid can be:

(squares in third grid) + 256 = 400

OR

256 + 400 = (squares in third grid)

We get this by applying the Pythagorean theorem.

So, the squares in the third grid can either be 144 or 656. And we only have 144 as an option, so that is your answer.

Your final answer is D. 144.