**Two pipes can fill a tank in 6hours and 8 hours .While a third pipe empties the full tank in 12hours.If all the three pipes are operate simultaneously, In how much time will the tank be filled ?**

A)4 hours

B)4hours 48min

C)5hours

D)5hours 48min

Answer

Option (b) is correct

**Explanation :**

1/6+1/8 – 1/12 =(4+3-2)/24

= 5/24

Time taken to fill the tank = 24/5 = 4hours 48min

**A tap can fill a tank in 6hrs.After half the tank is filled, three more similar taps are opened. What is the total time taken to fill the tank completely ?**

A)3hrs

B)3hrs 15 min

C)3hrs 45 min

D)4hrs

Answer

Option (c) is correct

**Explanation :**

Time taken to fill the half tank = 6/2 = 3 hrs.—(1/2 part is filled)

Remaining part = 1/2

Time taken to fill the remaining part =

= (3×1)/(2×2) = 3/4hrs

3/4 hrs = 45 min

Total time = 3hrs+45 min = 3hrs 45min

**Two pipes can fill a tank in 8 hours and 10 hours .If two pipes are operate simultaneously, In how much time will the tank be filled ?**

A)4hrs 18min

B)10min

C)4hrs

D)12hrs 10min

Answer

Option (a) is correct

**Explanation :**

1/(A+B) =1/8 + 1/10

= (10+8)/80 = 9/40

40/9=4hrs 18min to filled the tank

**Two pipes A and B can fill a tank in 20 minutes and 40 minutes.If both pipes are opened simultaneously , after how much time should B be closed so that the tank is full in 18 minutes ?**

A)10 min

B)4 min

C)8 min

D)7min

Answer

Option (b) is correct

**Explanation :**

A fill the tank in 1 minute (20×2 = 40) = 2 units

B fill the tank in 1 minute (40×1 = 40) = 1units

For 18 min(A) = 18×2 = 36 units

Remaining = 40 – 36 = 4 units

Time for B be closed so that the tank is full in 18 minutes = 4/1 = 4 min

**Three taps P,Q and R can fill a tank in 10,20 and 30 hours respectively. If A is open all the time and Q and R are open for one hour each alternatively ,the tank will be fill in**

A)7 hours

B)7 hours 30min

C)7hours 45min

D)7hours 20 min

Answer

Option (a) is correct

**Explanation :**

A+B in 1 hr =(1/10)+(1/20) = (2+1)/20 = 3/20

A+C in 1 hr =(1/10)+(1/30) = (3+1)/20 = 4/30

In 2 hr => (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)……1hour

Total time taken to fill the tank = 6+1 = 7 hours

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