- A10 min
- B8 min
- C9 min
- D12 min
Step-by-Step Solution
Each 2-minute cycle adds . After 4 cycles (8 min) it is full. In the 9th minute A adds and the tank is full. (12 min ignores that A can finish before B runs again.)
Answer: C) 9 min
Pipe A fills a tank in 3 minutes; pipe B empties it in 6 minutes. Starting with A, they are opened alternately for 1 minute each. When will the empty tank first be full?
Competition practicePipes & Cisterns
Master this topic in 30 minutes a day.
Don't just memorise the answer — build a daily practice habit.
Practice 5 Similar Questions Free →All Pipes & Cisterns practice questions
More Pipes & Cisterns practice
Pipes A, B and C together fill a tank in 6 hours. After 2 hours C is closed, and A and B…Pipe A fills a tank 8 minutes faster than pipe B. Together they fill it in 3 minutes.…Pipes A, B and C fill a tank in 10, 12 and 15 hours. A stays open throughout, while B…Three pipes fill a tank. The first two together take as long as the third alone. The…A cistern has pipes A and B that fill it in 3 hours and 4 hours, and pipe C that empties…