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1. Two pipes A and B can fill a tank in 15 minutes and 20 minutes respectively. Both the pipes are opended together but after 4 minutes, pipe A is turned off. What is the total time required to fill the tank?
- A. 10 min 20 sec
- B. 10 min 20 sec
- C. 10 min 20 sec
- D. 10 min 20 sec
Answer: Option D
Explanation:
By pipe A and B
Part filled in 4 minutes = 4×( 1/15 + 1/20) = 7/15
Remaining part = 1 - 7/15 = 8/15
part filled by B in 1 minute = 1/20
By B,
1/20 part can be filled in 1 minute
8/15 part can be filled in ( 20×8)o/15 = 10 min 40 sec
So, total time required ( 4 min + 10min 40 sec) = 14 min 40 sec.
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