1. A leak in the bottom of a tank can empty the full tank in 6 hours. An inlet pipe fills water at the rate of 4 litres a minute. When the tank is full, the inlet is opened and due to the leak the tank is empty in 8 hours. The capacity of the tank (in litres) is A) 5780 litres B) 5770 litres C) 5760 litres D) 5750 litres Ans. C Work done by the inlet in 1 hour = 16-18=124Work done by inlet in 1 min=124*160=11440=>Volume of 1/1440 part = 4 liters16-18=124Work done by inlet in 1 min=124*160=11440=>Volume of 1/1440 part = 4 liters16-18=124Work done by inlet in 1 min=124*160=11440=>Volume of 1/1440 part = 4 liters Volume of whole = (1440 * 4) litres = 5760 litres. 2. An electric pump can fill a tank in 3 hours. Because of a leak in the tank, it took 3 hours 30 min to fill the tank. In what time the leak can drain out all the water of the tank and will make tank empty ? A) 10 hours B) 13 hours C) 17 hours D) 21 hours Ans. D Work done for 1 hour without leak = 1/3 Work done with leak = 312=72Work done with leak in 1 hr= 27Work done by leak in 1 hr =13-27=121312=72Work done with leak in 1 hr= 27Work done by leak in 1 hr =13-27=121312=72Work done with leak in 1 hr= 27Work done by leak in 1 hr =13-27=121 So tank will be empty by the leak in 21 hours. 3. A tank can be filled by a tap in 20 minutes and by another tap in 60 minutes. Both the taps are kept open for 10 minutes and then the first tap is shut off. After this, the tank will be completely filled in what time ? A) 10 mins B) 15 mins C) 20 mins D) 25 mins Ans. C 4. A cistern can be filled in 9 hours but due to a leak at its bottom it takes 10 hours. If the cistern is full, then the time that the leak will take to make it empty will be ? A) 20 hours B) 19 hours C) 90 hours D) 80 hours Ans. C Part filled without leak in 1 hour = 1/9 Part filled with leak in 1 hour = 1/10 Work done by leak in 1 hour =19-110=190=19-110=190=19-110=190 So total time to empty the cistern is 90 hours 5. Taps A and B can fill a bucket in 12 minutes and 15 minutes respectively. If both are opened and A is closed after 3 minutes, how much further time would it take for B to fill the bucket? A) 8 min 15 sec B) 7 min 15 sec C) 6 min 15 sec D) 5 min 15 sec Ans. A Part filled in 3 minutes = 3*(112+115)=3*960=920Remaining part =1-920=1120=>115:1120=1:X=>X=1120*151=>X=8.25mins3*(112+115)=3*960=920Remaining part =1-920=1120=>115:1120=1:X=>X=1120*151=>X=8.25mins3*(112+115)=3*960=920Remaining part =1-920=1120=>115:1120=1:X=>X=1120*151=>X=8.25mins So it will take further 8 mins 15 seconds to fill the bucket.