Question

A rectangle has a length of 12 yards less than 3 times its width. If the area of the rectangle is 135 square yards, find the length of the rectangle.

Answer 1

Answer:

The length is 15 yards

Step-by-step explanation:

Given

Represent the width with W and length with L: So

$Area = 135yd^2$

$L=3W - 12$

Required

Determine the length of the rectangle:

Area is calculated as thus:

$Area = L * W$

Substitute 3W - 12 for L and 135 for Area

$135= (3W - 12) * W$

$135= 3W^2 - 12W$

Reorder:

$3W^2 - 12W - 135= 0$

Divide through by 3

$W^2 - 4W - 45 = 0$

Expand:

$W^2 - 9W + 5W - 45 = 0$

$W(W - 9) + 5(W - 9) = 0$

$(W + 5)(W-9) = 0$

$W + 5 = 0$ or $W - 9 = 0$

$W = -5$ or $W = 9$

But width can't be negative

So:

$W = 9$

Recall that: $L=3W - 12$

$L = 3 * 9 - 12$

$L = 15$

Hence, the length 15 yards