Kelly wants to create a rectangular playpen for his cats in his backyard, and estimates that the cats will need 500 square feet. He also wants the length of the playpen to be 20 feet longer than the width, so they have room to run. What dimensions should the playpen be?

Question

welshfella · Answer

let the width of the pen be x , so the length will be x + 20  feet

so the area 500 = x(x + 20)

solve this for x

welshfella · Answer

you'll get 2 values for x . The one you require will be positive. 
x willl be the width and x = 20 the length.