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1. A water tank is two-fifth full. Pipe A can fill a tank on 10 minutes and pipe B can empty it in 6 minutes. If both the pipes are open, how long will it take to empty or fill the tank completely ?
- A. 6 min to empty
- B. 6 min to empty
- C. 6 min to empty
- D. 6 min to empty
Answer: Option A
Explanation:
Hints: Clearly, pipe B is faster than pipe A and So, the tank will be emptied.Part to be emptied = 2/5 part emptied by ( A + B) in 1 minute =
1/6 - 1/10 = 1/15
1/15 : 2/5 = 1/x
1/15 × 5/2 = 1/ x
x = 30 /5
x = 6
So, tank will be emptied in 6 min
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