Answer:
25.92 ft
Explanation:
Since the area is 42:
A = B * H
Square root of 42 : 6.48074069841 (round down to 6.48)
Since the sandbox is a square, and we are looking for perimeter, multiply 6.48 * 4 = 25.92 ft
If you didn't round down to 6.48, it would not matter. When you round to the nearest hundreth, it still ends up being 25.92 ft.
6.48074069841 * 4 = 25.9229627936 (round down to 25.92)
You're welcome! :D