Question

A rectangular swimming pool is 10m wide and 15m long. The pool is surrounded by a deck of uniform width, whose area is equal to the area of the pool. How wide is the deck?

Answer 1

So the pool plus the deck is twice the area of the pool ...
(10+2w)(15+2w) = 2(10*15)

Answer 2

(10 + 2 w) (15 + 2w) = 2 * 10 * 15

150 + 50 w + 4 w^2 = 300

2 w^2 + 25 w - 75 = 0

(2 w - 5) (w + 15) = 0

2 w - 5 = 0

w + 15 = 0

Answer 3

1500 sq cm