4. Best Pools Ever is building a new community pool in Harlem. The pool is surrounded by a 2-foot wide walkway. The width of the pool is 23 feet less than the length of the pool. The total area enclosed by the outer edge of the walkway is 1674 ft 2 . What are the dimensions of the pool?

1 answer

To find the dimensions of the pool, let's define some variables.

Let:

  • \( L \) = length of the pool
  • \( W \) = width of the pool

According to the problem, we have the following relationships:

  1. The width of the pool is 23 feet less than the length of the pool: \[ W = L - 23 \]

  2. The total area enclosed by the outer edge of the walkway is 1674 square feet. The walkway is 2 feet wide, which means that the dimensions of the area including the walkway will be:

    • Length including walkway: \( L + 4 \) (2 ft on each side)
    • Width including walkway: \( W + 4 \) (2 ft on each side)

Thus, the area including the walkway can be expressed as: \[ \text{Area} = (L + 4)(W + 4) \] We know this area equals 1674 square feet: \[ (L + 4)(W + 4) = 1674 \]

Now we can substitute \( W \) from the first equation into this equation: \[ (L + 4)((L - 23) + 4) = 1674 \] This simplifies to: \[ (L + 4)(L - 19) = 1674 \]

Next, we will expand and simplify this equation: \[ L^2 - 19L + 4L - 76 = 1674 \] \[ L^2 - 15L - 76 = 1674 \] Now, bring 1674 to the left side: \[ L^2 - 15L - 1750 = 0 \]

Now, we will solve this quadratic equation using the quadratic formula, \( L = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \), where \( a = 1 \), \( b = -15 \), and \( c = -1750 \): \[ L = \frac{-(-15) \pm \sqrt{(-15)^2 - 4 \cdot 1 \cdot (-1750)}}{2 \cdot 1} \] \[ L = \frac{15 \pm \sqrt{225 + 7000}}{2} \] \[ L = \frac{15 \pm \sqrt{7225}}{2} \] Calculating \( \sqrt{7225} = 85 \): \[ L = \frac{15 \pm 85}{2} \]

Calculating the two potential solutions for \( L \):

  1. \( L = \frac{100}{2} = 50 \)
  2. \( L = \frac{-70}{2} = -35 \) (not physically meaningful)

Thus the valid length of the pool is \( L = 50 \) feet.

Now we can find the width of the pool: \[ W = L - 23 = 50 - 23 = 27 \text{ feet} \]

Therefore, the dimensions of the pool are:

  • Length: \( 50 \) feet
  • Width: \( 27 \) feet

To confirm, let's check the total area including the walkway:

  • Length including walkway: \( 50 + 4 = 54 \) feet
  • Width including walkway: \( 27 + 4 = 31 \) feet
  • Area: \( 54 \times 31 = 1674 \) square feet, which matches.

Thus, the dimensions of the pool are: \[ \boxed{50 \text{ feet (length)} \text{ and } 27 \text{ feet (width)}} \]