Delhi Police Constable Exam Model Paper 9

GIVEN:
A and B together can finish a work in 15 days and ratio of efficiency of A to B is 5 : 3.
CALCULATION:
Ratio of efficiency of A to B = 5 : 3
Ratio of time taken by A to B = 3 : 5
Let time taken by A and B alone to finish the work is ‘3x’ and ‘5x’ respectively.
Now,
$\frac{1}{3\mathit{x}}+\frac{1}{5\mathit{x}}=\frac{1}{15}$
⇒ $\frac{5+3}{15\mathit{x}}=\frac{1}{15}$
⇒ x = 8
∴ Time taken by A alone to finish the work $=3\mathit{x}=24$ days