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Q.1 There are three inlets P,Q & R attached with a tank. If P & Q are opened then tank is filled in 120hr & if P & Q are opened then tank is filled in 90 hr. Find the time in which P,Q & R can fill the tank, if these all are opened ?
A) 60 h
B) 61 h
C) 62 h
D) 63 h
Ans. A
Shortcut :
2xyz / xy + yz + zx
2*72*120*90 / 25920 = 60 h

Q.2 Because of a hole in a bottom of a tank , a tank becomes empty in 6 min. after opening a tap which fills the tank at the rate of 8 lit/min the tank is emptied in  10 min. Find the capacity of the tank ?

A) 117 litre

B) 118 litre

C) 119 litre

D) 120 litre

Ans. D

Shortcut :
abc / c-a
i.e. 6*8*10 / 10-6 = 120 litre

Q.3 Two pipes can separately fill a tank in 10 hr & 15 hr. Both the pipes are opened to fill the cistern but when the tank is 1/3rd full a leak develops in the tank through which 1/3rd of water supplied but both the pipes leak out . What is the total time taken to fill the tank ?

A) 6 hr.

B) 10 hr.

C) 12 hr.

D) 15 hr.

Ans.  A

Time taken by the two pipes to fill the tank:
10*15/10+15
=6 hr.

Q.4 A pipe can fill a bath in 20 minutes and another can fill it in 30 minutes. A person opens both the pipes simultaneously. When the bath should have been full, he finds that the waste pipe was open. He then closes the waste pipe and in 3 more minutes the bath is full. In how much time would the waste pipe empty it?
A) 50 min
B) 48 min
C) 44 min
D) 38 min

Ans. B

First pipe can fill the cistern = 20 min
Second pipe fill the cistern = 30 min.
But together both pipes can fill it =   = 12 min
Now according to question
12  = 1
{Where x = Time taken by leak to empty the cistern}
1 –   = 1
x = 48 min

Q.5 A supply of water lasts for 15 days if 12 gallons leak off everyday, but only for 100 days if 15 gallons leak off daily . What is the total quantity of water in the supply ?
A) 900
B) 1125
C) 3350
D) 1250
Ans. A
consumption be x and supply y:
150x + 12*150 = y ....(i)
100x + 15*100 = y ....(ii)
multiply i by 2 and ii by 3 and equate,
4500 - 3600 = 3y - 2y
y = 900

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