Given that the backyard is rectangular and the length is 56 feet while the area is 1400 square feet. Recall that the area A of a rectangle is the product of the length L and the width B.
A = L * B
Hence the width B may be found from
1400 = 56 * B
B = 1400/56
B = 25 feet
b. If the fencing cost $10 per foot then because a rectangle has two lengths and two widths,
the total cost to fence the backyard will be
= $10 * 2(56 + 25)
= $1,620
