41.  Two pipes A and B can separately fill a tank in 10 and 15 minutes respectively. A third pipe C can drain off 30 liters of water per minute. If all the pipes are opened, the tank can be filled in 10 minutes. What is the capacity of the tank?


500 liters
370 liters
450 liters
320 liters


Answer

 Option

1/10+1/15-1/x = 1/10 X= 15 15*30 = 450 liters

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42.  A tank is filled by 3 pipes with uniform flow.The first 2 pipes operating simultaneously fill the tank in the same time during which the tank is filled by the 3'rd pipe alone.The 2'nd pipe fills the tank 5 hrs faster than the 1'st pipe and 4 hrs slower than the 3'rd pipe.The time required by the first pipe is?


6 hrs
10 hrs
15 HRS
30 HRS


Answer

 Option

SUPPOSE 1'st pipe alone takes x hrs.To fill the tank than 2'nd & 3'rd pipes will take (x-5) & ( x-9) hrs respectively to fill the tank. therefore 1/x+1/(x-5) = 1/(x-9) = x-5 +x / x(x-5) = 1/(x-9) (2x-5) (x-9) =x(x-5) = x (x-5) = x^2 -18x +45 =0 (x-15) (x-3) = 0 = x=15

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43.  3 tapes A,B & C can fill a tank in 12,15 and 20 hrs respectively.If A is open all the time and B and C are open for 1 hr each alternately ,the tank shall be full in?


6 hrs
6 2/3 hrs
5 hrs
7 hrs


Answer

 Option

(A+B)'s 1 hour work = (1/12 + 1/15) = 9/60 = 3/20 (A+C)'s 1 hour work = (1/12+1/20) = 8/60 = 2/50 Part filled in 2 hrs = (3/20+2/15) = 17/60 : part filled in 6 hrs = (3*17/60) = 17/20 Remaining part =( 1-17/20) = 3/20 Now it is the turn off A and B and 3/20 part is filled by A & B in 1 hr therefore total time taken to fill the tank = (6+1) hrs = 7 hrs.

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44.  A water tank is 2/5th full.Pipe A can fill a tank in 10 mins and pipe B can empty it in 6 mins. If both the pipes are open,how long will it take to empty or fill the tank completely?


6 mins to empty
6 mins to fill
9 mins to empty
None of these


Answer

 Option

clearly pipe B is faster than Pipe A and so the tank will be emptied. Part to be emptied = 2/5 Part emptied by (A+B) in 1 minute = (1/6 - 1/10) = 1/15 hence 1/15 : 2/5 : :1:x or x=(2/5*1*15) = 6 mins so the tank will be emptied in 6 mins

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45.  2 pipes can fill a tank in 20 and 24 mins respectively. And a waste pipe can empty 3 gallons per minute.All the 3 pipes working together can fill the tank in 15 minutes.The capacity of the tank is ?


60 gallons
100 gallons
120 gallons
180 gallons


Answer

 Option

Work done by the waste pipe in 1 minute = 1/15 - (1/20 + 1/24) = ( 1/15 - 11/120) = (- 1/40 (negative sign means emptying) Therefore volume of 1/40 part = 3 gallons. Volume of whole = (3*40) gallons = 120 gallons.

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