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02 Dec 2020, 12:15
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C
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Difficulty:
95%
(hard)
Question Stats:
50% (03:09) correct
50%
(03:29)
wrong
based on 32
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A cylindrical overhead tank is filled by two pumps P1 and P2. P1 can fill the tank in 8 hr while P2 can fill the tank in 12 hr. There is a pipe P3 which can empty the tank in 8 hr. Both the pumps are opened simultaneously. The supervisor of the tank, before going out on a work, sets a timer to open P3 when the tank is half filled so that the tank is exactly filled up by the time he is back. Due to technical fault P3 opens when the tank is one-third filled. If the supervisor comes back as per the plan what percent of the tank is till empty?
A. 15%
B. 12%
C. 10%
D. 8%
E. 6%
Are You Up For the Challenge: 700 Level Questions
A. 15%
B. 12%
C. 10%
D. 8%
E. 6%
Are You Up For the Challenge: 700 Level Questions
Answer C
14.28%(little variable will be because at last, I am playing with time) that attempt to reduce my time for answer the question did not work so let us stick to the standard method 1.2 hrs was the difference between 9.6-8.4 at a rate of 2 so the water left to fill the tank will be 1.2*2=2.4 that is 10% of our tank.
14.28%(little variable will be because at last, I am playing with time) that attempt to reduce my time for answer the question did not work so let us stick to the standard method 1.2 hrs was the difference between 9.6-8.4 at a rate of 2 so the water left to fill the tank will be 1.2*2=2.4 that is 10% of our tank.
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03 Dec 2020, 06:45
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Let's say the tank has a capacity of 24L
Then, Rate of Pump A = 3 L/hr
Rate of Pump B = 2 L/hr
Rate of Pump C = -3 L/hr
time elapsed when the tank is halfway full(12L) = 12/(3+2) = 2.4 hrs
When the third pump is turned on, new rate is (3+2-3) = 2 L/hr
Time when the supervisor is back = (12/2)+2.4 = 8.4 Hrs
If the pump switches only when a third of the tank is full(8L) then time elapsed until then = 8/5 = 1.6 hrs
Since the manager returns after 8.4 hrs, the pumps have 6.8 hrs to run.
also, the rate of pumps after third pump is switched on is 2 L/hr.
Therefore, in 6.8 hrs the pumps will fill 13.6L (6.8x2) of the tank.
Add to that 8L already filled earlier, we get 21.6L. Leaving 2.4L or 10% of the tank empty
Answer: C
Then, Rate of Pump A = 3 L/hr
Rate of Pump B = 2 L/hr
Rate of Pump C = -3 L/hr
time elapsed when the tank is halfway full(12L) = 12/(3+2) = 2.4 hrs
When the third pump is turned on, new rate is (3+2-3) = 2 L/hr
Time when the supervisor is back = (12/2)+2.4 = 8.4 Hrs
If the pump switches only when a third of the tank is full(8L) then time elapsed until then = 8/5 = 1.6 hrs
Since the manager returns after 8.4 hrs, the pumps have 6.8 hrs to run.
also, the rate of pumps after third pump is switched on is 2 L/hr.
Therefore, in 6.8 hrs the pumps will fill 13.6L (6.8x2) of the tank.
Add to that 8L already filled earlier, we get 21.6L. Leaving 2.4L or 10% of the tank empty
Answer: C
