Question

A is thrice as efficient as B and hence completes a work in 40 days less than the number of days taken by B. What will be the number of days taken by both of them when working together?

• A. 22.5 days
• B. 15 days
• C. 20 days
• D. 18 days
• E. None of these

Answer 1

The correct option is B

15 days

Let efficiency of B be x
Days are inversely proportional to efficiency.
According to question:
$\Rightarrow 3x-x=40\Rightarrow 2x=40\therefore x=20$
Time taken by A = x days = 20 days
Time taken by B = 3x days = $3\times 20=60days$
Time taken by A and B together $=\frac{20\times 60}{80}=15days$