Answer:
[tex]60\ \dfrac{ft^2}{h}.[/tex]
Step-by-step explanation:
If a windowpane is of the width of 5 feet and the length of 3 feet, then the area of this windowpane is
[tex]A_{windowpane}=\text{length}\cdot \text{width}=3\cdot 5=15\ ft^2.[/tex]
If Edward cleaned a windowpane in 1/4 of an hour, then he cleaned 15 square feet in 1/4 of an hour. Thus, the speed at which Edward cleaned the pane is
[tex]\dfrac{15}{\frac{1}{4}}=15\cdot 4=60\ \dfrac{ft^2}{h}.[/tex]
