**1.**

**Two pipes A**

and B can fill a tank in 36 hours and 45 hours respectively. If both

the pipes are opened simultaneously, how much time will be taken to fill the

and B can fill a tank in 36 hours and 45 hours respectively. If both

the pipes are opened simultaneously, how much time will be taken to fill the

**tank?**

(1)

20 hours

(3) 15 hours (4)

25 hours

20 hours

**(2) 30 hours**(3) 15 hours (4)

25 hours

**2.**

**Two pipes**

can fill a tank in 10hours and 12 hours respectively while a third, pipe

empties the full tank in 20 hours. If all the three pipes operate

simultaneously, in how much time will the tank be filled?

can fill a tank in 10hours and 12 hours respectively while a third, pipe

empties the full tank in 20 hours. If all the three pipes operate

simultaneously, in how much time will the tank be filled?

(1) 8 hrs 30 min (2)

7 hrs 30 min

7 hrs 30 min

(3) 8

hrs 38 min (4) 7 hrs 38 min

hrs 38 min (4) 7 hrs 38 min

**3.**

**If two pipes**

function simultaneously, the reservoir will be filled in 12 hours. One

pipe fills the reservoir 10 hours faster than the other. How many hours does

it take the second pipe to fill the reservoir?

function simultaneously, the reservoir will be filled in 12 hours. One

pipe fills the reservoir 10 hours faster than the other. How many hours does

it take the second pipe to fill the reservoir?

(1) 10

hours (2) 40 hours

hours (2) 40 hours

(3) 30 hours (4) 20 hours

**4.**

**Two pipes A,B can fill a tank in 24 min. and 32**

min. respectively. If both the pipes are opened simultaneously, after how much

time B should be closed so that the tank is full in 18 min.?

min. respectively. If both the pipes are opened simultaneously, after how much

time B should be closed so that the tank is full in 18 min.?

(1) 8 min (2)

12 min

12 min

(3) 15 min (4) 20

min

min

**5.**

**Two pipes A and B can fill a tank in 36 min. and 45**

min. respectively. A water pipe C can empty the tank in 30 min. First A and B

are opened. After 7 min, C is also opened. In how much time, the tank is full?

(1) 39 min (2)

min. respectively. A water pipe C can empty the tank in 30 min. First A and B

are opened. After 7 min, C is also opened. In how much time, the tank is full?

40 min

(3) 42 min (4) 38

min

min

**6.**

**Two pipes**

can fill a cistern in 14 hours and 16 hours respectively. The pipes

can fill a cistern in 14 hours and 16 hours respectively. The pipes

**are**

opened simultaneously and it is found that due to leakage in the bottom it

took 32 minutes more to fill the cistern. When the cistern is full, in what

time will the leak empty it?

opened simultaneously and it is found that due to leakage in the bottom it

took 32 minutes more to fill the cistern. When the cistern is full, in what

time will the leak empty it?

(1) 112 min

**(2)**

115 min

(3) 120 min (4)

110 min

110 min

**7.**

**An electric pump can fill a tank in 3 hours.**

Because of a leak in , the tank it took 3(1/2) hours to fill the tank. If

the tank is full, how much time will the leak take

Because of a leak in , the tank it took 3(1/2) hours to fill the tank. If

the tank is full, how much time will the leak take

**to empty it?**

(1) 28

hours (2) 25 hours

hours (2) 25 hours

(3) 21

hours (4)

20 hours

hours (4)

20 hours

**8.**

**A cistern has two taps which fill it in 12 minutes**

and 15minutes respectively. There is also a waste pipe in the cistern. When all

the 3 are opened, the empty cistern is full in 20 minutes. How long will the

waste pipe take to empty the full cistern?

and 15minutes respectively. There is also a waste pipe in the cistern. When all

the 3 are opened, the empty cistern is full in 20 minutes. How long will the

waste pipe take to empty the full cistern?

(1) 20min (2)

40 min

40 min

(3) 30 min (4) 10

min

min

**9.**

**Three**

pipes A, B and C can fill a tank in 6 hours. After working at it together for 2

hours, C is closed and A and B can fill the remaining part in 7 hours. The

number of hours taken by C alone to fill the tank is:

pipes A, B and C can fill a tank in 6 hours. After working at it together for 2

hours, C is closed and A and B can fill the remaining part in 7 hours. The

number of hours taken by C alone to fill the tank is:

(1) 10 (2) 14

(3) 12 (4)

12

12

**10.**

**A**

tap can fill a tank in 6 hours. After half the tank is filled, three more

similar taps are opened. What is the total time taken to fill the tank

completely?

tap can fill a tank in 6 hours. After half the tank is filled, three more

similar taps are opened. What is the total time taken to fill the tank

completely?

(1) 3 hours 15 min (2)

3 hours 45 min

3 hours 45 min

(3) 3 hours 40 min (4)

3 hours 50 min

3 hours 50 min

**ANSWERS WITH EXPLANATIONS:**

**1.**(1)

**Explanation**

:

:

Part filled

by A in 1 hour = (1/36);

Part filled by B in 1 hour = (1/45);

Part filled by (A + B) In 1 hour =(1/36)+(1/45)=(9/180)=(1/20)

Hence, both the pipes together will fill the tank in

by A in 1 hour = (1/36);

Part filled by B in 1 hour = (1/45);

Part filled by (A + B) In 1 hour =(1/36)+(1/45)=(9/180)=(1/20)

Hence, both the pipes together will fill the tank in

**20 hours.**

**2.**

(2)

**Explantion:**

Net part

filled In 1 hour =(1/10)+(1/12)-(1/20)=(8/60)=(2/15).

The tank will be full in

filled In 1 hour =(1/10)+(1/12)-(1/20)=(8/60)=(2/15).

The tank will be full in

__15/2__hrs**= 7 hrs 30 min.**

**3.**

(3)

**Explanation**:

let the

reservoir be filled by first pipe in x hours.

Then ,second pipe fill it in (x+10)hrs.

Therefore (1/x)+(1/x+10)=(1/12)

reservoir be filled by first pipe in x hours.

Then ,second pipe fill it in (x+10)hrs.

Therefore (1/x)+(1/x+10)=(1/12)

(x+10+x)/(x(x+10))=(1/12).

x^2 –14x-120=0

x^2 –14x-120=0

(x-20)(x+6)=0

x=20 [neglecting the negative value of x]

so, the second pipe will

(i.e)

x=20 [neglecting the negative value of x]

so, the second pipe will

**take (20+10)hrs**.(i.e)

**30****hours**to fill the reservoir**4.**

(1)

**Explantion**:

let B be

closed after x min. then ,

Part filled by (A+B) in x min. +part filled by A in (18-x)min.=1

Therefore x*((1/24)+(1/32))+(18-x)*(1/24)=1

closed after x min. then ,

Part filled by (A+B) in x min. +part filled by A in (18-x)min.=1

Therefore x*((1/24)+(1/32))+(18-x)*(1/24)=1

(7x/96) +

((18-x)/24)=1.

7x +4*(18-x)=96.

Hence, be must be closed after 8 min.

((18-x)/24)=1.

7x +4*(18-x)=96.

Hence, be must be closed after 8 min.

**5.**

(1)

**Explanation:**

Part filled

in 7 min. = 7*((1/36)+(1/45))=(7/20).

Remaining part=(1-(7/20))=(13/20).

Net part filled in 1min. when A,B and C are opened=(1/36)+(1/45)-(1/30)=(1/60).

Now,(1/60) part is filled in one minute.

(13/20) part is filled in (60*(13/20))=

in 7 min. = 7*((1/36)+(1/45))=(7/20).

Remaining part=(1-(7/20))=(13/20).

Net part filled in 1min. when A,B and C are opened=(1/36)+(1/45)-(1/30)=(1/60).

Now,(1/60) part is filled in one minute.

(13/20) part is filled in (60*(13/20))=

**39****minutes**.**6.**

(1)

**Explanation:**

Work done

by the two pipes in 1 hour =(1/14)+(1/16)=(15/112).

Time taken by these pipes to fill the tank = (112/15)hrs = 7 hrs 28 min.

Due to leakage, time taken = 7 hrs 28 min + 32 min = 8 hrs

Work done by (two pipes + leak) in 1 hour = (1/8).

Work done by the leak m 1 hour =(15/112)-(1/8)=(1/112).

Leak will empty the full cistern in

by the two pipes in 1 hour =(1/14)+(1/16)=(15/112).

Time taken by these pipes to fill the tank = (112/15)hrs = 7 hrs 28 min.

Due to leakage, time taken = 7 hrs 28 min + 32 min = 8 hrs

Work done by (two pipes + leak) in 1 hour = (1/8).

Work done by the leak m 1 hour =(15/112)-(1/8)=(1/112).

Leak will empty the full cistern in

**112****hours**.**7.**

(4)

**Explanation:**

work done

by the leak in 1 hour=(1/3)-(1/(7/2))=(1/3)-(2/7)=(1/21).

The leak will empty .the tank in

by the leak in 1 hour=(1/3)-(1/(7/2))=(1/3)-(2/7)=(1/21).

The leak will empty .the tank in

**21****hours**.**8.**

(4)

**Explanation**:

Work done

by the waste pipe in 1min

=(1/20)-(1/12)+(1/15) = -1/10 [negative sign means emptying]

therefore the waste pipe will empty the full cistern in

by the waste pipe in 1min

=(1/20)-(1/12)+(1/15) = -1/10 [negative sign means emptying]

therefore the waste pipe will empty the full cistern in

**10min**

**9.**

(2)

**Explanation**: (A+B+C) – (A+B) can give you the

answer.

(A+B+C) =1/6 and (A+B+C) in 2hrs=2/6 and remaining part 1-2/6=2/3.

So (A+B) in 7 hrs is 2/ (3*7) =2/21.

1/6-2/21=1/14 so answer is

**14**.

**10.**

(2)

**Explanation**:

A tap can fill a tank in 6 hours.

After half the tank is filled i.e. after 3 hrs.

three more similar taps are opened i.e.

no. of taps to fill remaining half tank = 4 taps

when 1 tap is used = (3 hrs/1 tap)

when 4 taps are used = (3 hrs/4 taps)=45min

total=

After half the tank is filled i.e. after 3 hrs.

three more similar taps are opened i.e.

no. of taps to fill remaining half tank = 4 taps

when 1 tap is used = (3 hrs/1 tap)

when 4 taps are used = (3 hrs/4 taps)=45min

total=

**3hrs+45min**