Question

R and S are employed to fill a cistern. R fills 4 litres in 3 minutes and S fills 3 litres in 4 minutes. In how much time will they fill 75 litres when working together?
1. 16 minutes
2. 36 minutes
3. 42 minutes
4. 14 minutes

Answer 1

Correct Answer - Option 2 : 36 minutes

Given:

R fills 4 litres in 3 minutes and S fills 3 litres in 4 minutes.

Formula Used:

Time = Work/ efficiency

Calculation:

Per minute efficiency of R = 4/3 litre/min

Per minute efficiency of S = 3/4 litre/min

Total Per minute efficiency of R and S = (¾ +4/3) litre/min = 25/12 litre/min

Time taken by R and S to fill 75 litres when working together = 75/(25/12)

= 75 × 12/25

= 3 × 12

= 36 minutes