Question

Sally painted a picture that has an area of 480 square inches. The length of the painting is 1 1/5 its width. Which of the following could be the dimensions of Sally’s painting? A. 20 inches by 24 inches B. 12 inches by 40 inches C. 16 inches by 30 inches D. 15 inches by 32 inches

Answer 1

A = 480
W = x
L = 11/5*x
therefore 480 = 11/5*x*x
480 = 11/5x^2
480*5 = 11x^2
2400/11 = x^2
$+ or-\sqrt{2400/11} = x$
However we can't have a negative width so width is $\sqrt{2400/11}$
Sub this into the length equation to find length $\frac{11}{5} * \sqrt{2400/11}$