A 40-foot by 10-foot rectangular garden is enclosed by a fence. To make the garden larger, while using the same amount of fencing, its shape is changed to a square. How many square feet larger than the old garden is the new garden?

Answer 1

old area = 400 ft^2

perimeter = 20+80 = 100
so
4 s = 100
s = 25

s^2 = area = 625

625 - 400 = ???

Answer 2

40 * 10 = 400 square feet

The fence is 100 feet long

25 * 25 = 625 square feet