If Ben

If Ben is ⅕ the age of his father, ¼ the age of his mother, and twice the age of his sister, how old are his parents and sister if he is eight years old?

Correct answer:

F =  40
M =  32
S =  4

Step-by-step explanation:

$$\begin{gathered} B=8 \\ B=F/5 \\ F=5\cdot B=5\cdot 8=40 \end{gathered}$$

$$\begin{gathered} B=\frac{1}{4}\cdot M \\ M=4\cdot B=4\cdot 8=32 \end{gathered}$$

$$\begin{gathered} B=2\cdot S \\ S=B/2=8/2=4 \end{gathered}$$

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