Question

If 18 boys can complete a piece of work in 3 days, then find the time required to complete the same work by 9 girls.

• A. 6 days
• B. 10 days
• C. 9 days
• D. 12 days

Answer 1

The correct option is A 6 days

The number of girls (N) employed to complete a piece of work is inversely proportional to the number of days (D).

$\Rightarrow N\propto \frac{1}{D}$

Let the constant of variation be k.
$\Rightarrow N=\frac{k}{D}$
$\Rightarrow ND=k$
Given, when N = 18 girls , D = 3 days.
So, $k=ND=\left(18\right)\left(3\right)=54$
$\Rightarrow N=\frac{54}{D}$
Hence, the time required (D) to complete the same work by 9 girls $=\frac{54}{N}=\frac{54}{9}=6days.$