Answer:
10
Explanation:
The ration is 1 : 4, so since the larger square has an area of 400, the smaller square has an area of 100. This makes the ratio 100 : 400, which is equal to 1 : 4 (all I did was multiple both sides of the ration by 100). Then, because a square has equal sides, I found the square root of 100. 10 is the square root of 100, because 10 x 10 = 100, so each side is 10 inches long.