Answer:
W ≈ 5.2 cm
Step-by-step 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
