2002 · Q62
Two pipes 'A' and 'B' can fill a tank in 15 minutes and 20 minutes respectively. Both the pipes are opened together but after 4 minutes, pipe 'A' is turned off. What is the total time required to fill the tank?
General Mental Ability, Quantitative Aptitude and StatisticsTime, work and measurement
- A12 mt 30 sec
- B14 mt 40 sec
- C10 mt 20 sec
- D11 mt 45 sec
Explanation
In 4 minutes both pipes fill 4×(1/15 + 1/20) = 4×7/60 = 7/15 of the tank. The remaining 8/15 is filled by B alone at 1/20 per minute: (8/15)÷(1/20) = 160/15 = 32/3 minutes = 10 min 40 s. Total time = 4 min + 10 min 40 s = 14 min 40 s — option (B).