Question

A rectangle with an area of 81 cm² has a length that is 3 times the width. How long is the width of the rectangle? Round to the nearest tenth.

Answer 1

W ≈ 5.2 cm

Explanation:

Represent the length and width by L and W respectively.

Then L * W = 81 cm^2, and L = 3W.

Substituting 3W for L in the first equation, we get:

3W * W - 81 = 0, or 3W^2 - 81 = 0.

To make it easier to find the final answer, rewrite 3W^2 - 81 = 0 as

81

W^2 = ------- = 27

3

Then W (the width) is the positive square root of 27, or W ≈ 5.2 cm

Answer 2

60.75 ≈ 60.8

Explanation:

4u-> 81

1u -> 20.25 (width)

3u-> 60.75 (length)