Question

Pushkin, Qutub and Ravinder together finish a task in 4 days. Ravinder and Samrat together finish it in 6 days. Qutub alone takes 20 days and Ravinder alone takes 10 days. In how many days can Pushkin and Samrat together finish the task?

• A. 8
• B. 5
• C. 6
• D. 4

Hint:

Convert the whole job into a convenient number of "work units" (a common multiple of all the days given) instead of working with fractions.

Answer 1

The Correct Option is C

Combined rate of P+Q+R \(=\frac{1}{4}\). So Pushkin \(=\frac{1}{4}-\frac{1}{20}-\frac{1}{10}=\frac{5-1-2}{20}=\frac{2}{20}=\frac{1}{10}\). From R+S \(=\frac{1}{6}\): Samrat \(=\frac{1}{6}-\frac{1}{10}=\frac{5-3}{30}=\frac{2}{30}=\frac{1}{15}\). Pushkin+Samrat \(=\frac{1}{10}+\frac{1}{15}=\frac{3+2}{30}=\frac{5}{30}=\frac{1}{6}\). Time \(=6\) days. Correct option: 6.