A tap can fill up a tank of 1250 litres in 4 hours, whereas another tap can fill the same tank in 8 hours. An outlet tap can empty that tank in 6 hours. If all the three taps are opened simultaneously, then how much time will it take to fill the tank completely?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 4.8 hours.
Time taken by tap A to fill the tank = 4 hours
Tank filled by tap 1 in one hour = 1/4 part of the tank
Time taken by tap B to fill the tank = 8 hours
Tank filled by tap 2 in one hour = 1/8 part of the tank
Time taken by tap C to empty the tank = 6 hours
Tank emptied by tap 3 in one hour = 1/6 part of the tank
So, the part of the tank filled in one hour when all three taps are opened simultaneously = 1/4 + 1/8 – 1/6
= (6 + 3 – 4)/ 24
= 5/24
Thus, time taken by 3 taps to fill the tank = 24/5 = 4.8 hours