Question

Eric loves Ed’s oatmeal for breakfast. He eats it at a constant rate of $\frac{2}{5}ozperminute.$ If he has eaten $8oz$ of oatmeal, how many hour(s) ago did he start eating?

• A. $\frac{1}{2}$
• B. $\frac{1}{3}$
• C. $\frac{1}{4}$
• D. $\frac{1}{5}$

Answer 1

The correct option is B $\frac{1}{3}$

Let time spent on eating is $T,$ then
Quantity eaten $=$ rate of eating $\times T$
$\Rightarrow 8oz=\frac{2}{5}\frac{oz}{min}\times T\Rightarrow \frac{8oz}{\frac{2}{5}\frac{oz}{min}}=\frac{\frac{2}{5}\frac{oz}{min}}{\frac{2}{5}\frac{oz}{min}}\times T\Rightarrow 8\times \frac{5}{2}min=T\Rightarrow T=20min\Rightarrow T=\frac{20min}{60min/hr}\Rightarrow T=\frac{1}{3}hr$