Time and Work Practice Test 5 with solutions

Ratio of efficiency of P and Q = $\frac{7}{4}$ : 1 = 7 : 4
Hence, ratio of their time taken = 4 : 7
Let P and Q can finish the job in 4x and 7x days respectively,
then, $\frac{1}{4\mathit{x}}+\frac{1}{7\mathit{x}}$ = $\frac{1}{7}$ ⇒ $\frac{11}{28\mathit{x}}$ = $\frac{1}{7}$
⇒ $\frac{1}{\mathit{x}}$ = $\frac{1}{7}\times \frac{28}{11}$ = $\frac{4}{11}$
x = $\frac{11}{4}$
The job can be done by P alone in 4 × $\frac{11}{4}$ = 11 days.