9514 1404 393
Answer:
 216 feet
Explanation:
The area is given by the formula ...
 A = LW
Solving for width, we have ...
 W = A/L = 2835 ft²/(45 ft) = 63 ft
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The perimeter is given by the formula ... 
 P = 2(L +W)
 P = 2(45 ft +63 ft) = 2(108 ft)
 P = 216 ft
216 feet of fencing are needed to enclose the area.