Chapter 10 - Systems of Equations and Inequalities - Section 10.1 Systems of Linear Equations: Substitution and Elimination - 10.1 Assess Your Understanding - Page 735: 55

$\text{Length = 30 ft and Width = 15 ft}$

Let us consider that $x$=width (in feet) and $y$=length (in feet). We are given: $y=2x~~~(1) $ and the perimeter is: $2x+2y=90~~~(2)$ Plug equation (1) into equation (2) to solve for $x$; then we get: $2x+(2)(2x)=90 \implies x=15$ Now, back substitute the value of $x$ into Equation (1) to solve for $y$: $y=(2)(15) \implies y=30$ Therefore, the dimensions of the floor are: $\text{Length = 30 ft and Width = 15 ft}$