11.  Two pipes can fill a tank in 4 hours and 12 hours.If two pipes are operate simultaneously, in how much time will the tank be filled?

3 hrs 10 min
13 hrs
3 hrs
None of these

```Answer

Answer: Option  C Explanation:(A+B) = 1/4+1/12 = (3+1)/12 = 4/12 = 1/3
3 hours to filled the tank. ```

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12.  Two the pipes fill the tank in 12 minutes and 15 minutes. There is also a waste pipe in the tank. When all the three are opened, the empty tank is full in 20 minutes.How long will the waste pipe take to empty the tank?

10 minutes
20 minutes
30 minutes
35 minutes

```Answer

Answer: Option  A Explanation:(1/20) - ( (1/12)+(1/15)) = (1/20) - ((5+4)/60) = (3-9)/60 = - 6/60
= -1/10 = 10 minutes. ```

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13.  10 buckets of water fill a tank when the capacity of each tank is 11.5 liters. How many buckets will be needed to fill the same tank, if the capacity of each bucket is 5 liters?

21
32
23
22

```Answer

Answer: Option  C Explanation:Capacity of the tank = 10* 11.5 = 115
capacity of bucket = 5 liters
Number of bucket needed = 115/5 = 23. ```

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14.  One pipe can fill a tank twice as fast as another pipe.If together the two pipes can fill the tank in 12 minutes, then the slower pipe alone will able to fill the tank in?

30 minutes
33 minutes
36 minutes
35 minutes

```Answer

Answer: Option  C Explanation:(1/x) + (1/2x) = (1/12)
(3/x) = (1/12) => (x/3) = 12
x= 36 minutes. ```

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15.  3 taps P, Q and R can fill a tank in 10,20 and 30 minutes respectively.If A is open all the time and Q and R are open for 1 hour each alternatively the tank will be fill in?

7 hrs
7 hrs 30 mins
8 hrs
7 hrs 50 mins

```Answer

Answer: Option  A Explanation:A+B in 1 hour = (1/10)+1/20) = (2+1)/20 = 3/20
A+C in 1 hour =(1/10)+(1/30)=(3+1)/20 = 4/30
In 2 hour => (3/20) + (4/30) = (9+8)/60 = 17/60
part filled in 6 hours = 3*(17/60) = 17/20
Remaining part = 1- (17/20) = (20-17)/20 = 3/20 (filled by A and B) ........ 1 hour
total time taken to fill the tank = 6+1 = 7 hours. ```

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