46.  Pipe A can fill a tank in 5 hrs, Pipe B in 10 hrs and Pipe C in 30 hrs.If all the pipes are open in how many hours will the tank be filled?

2 hrs
2.5 hrs
3 hrs
3.5 hrs

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Answer: Option  C Explanation:Part filled by ( A+B+C) in 1 hr = (1/5+1/10+1/30) = 1/3
therefore all the 3 pipes together will fill the tank in 3 hrs ```

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47.  A water tank is 2/5th full.Pipe A can fill a tank in 10 mins and pipe B can empty it in 6 mins. If both the pipes are open,how long will it take to empty or fill the tank completely?

6 mins to empty
6 mins to fill
9 mins to empty
None of these

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Answer: Option  A Explanation: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
hence 1/15 : 2/5 : :1:x or x=(2/5*1*15) = 6 mins
so the tank will be emptied in 6 mins ```

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48.  A tape can fill a tank in 6hrs.After half the is filled 3 more similar tapes are opened.What is total time taken to fill the tank completely?

3hrs 15 minutes
3hrs 45 mins
4 hrs 15 mins
4 hrs

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Answer: Option  B Explanation:Time taken by 1 tape to fill half the tank = 3hrs.
Part filled by the 4 tapes in 1 hr = (4*1/6) = 2/3.
Remaining part = (1-1/2) = 1/2
2/3: 1/2: 1: x or x =(1/2*1*3/2) = 3/4 hrs i.e.45 minutes
so total time taken 3 hrs 45 mins. ```

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49.  A cistern can be filled by a tape in 4 hrs while it can be emptied by another tape in 9 hrs. If both the tapes are opened simultaneously then after how much time will the cistern get filled?

4.5 hrs
5 hrs
6.5 hrs
7.2 hrs

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Answer: Option  D Explanation:Net part filled in 1 hr = (1/4 - 1/9) = 5/36.
The cistern will be filled in 36/5 hrs i.e. 7.2 hrs ```

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50.  Two pipes A & B can fill a tank in 20 and 30 minutes respectively.If the both pipes are used together,then how long will it take to fill the tank?

12 mins
15 mins
25 mins
50 mins

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Answer: Option  A Explanation:Part filled by A in 1 minute  = 1/20; Part filled by B in 1 minute = 1/30.
Part filled by (A+B) in 1 minute.
(A+B) = (1/20+1/30) = 1/12.
Hence both the pipes can fill the tank in 12 minutes ```

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