A rectangular tank, which has a height of 30 cm and can hold 60 litres of water, was empty at first. Tap X was turned on to fill the tank with water at a rate of 4 litres per minute. After 1 minute, Tap Y was turned on to drain the water from the tank at a rate of 3 litres of water per minute. Both taps were turned off 8 minutes after Tap Y was turned on. What was the height of the water level in the tank when both taps were turned off?
Originally posted by Ngml:A rectangular tank, which has a height of 30 cm and can hold 60 litres of water, was empty at first. Tap X was turned on to fill the tank with water at a rate of 4 litres per minute. After 1 minute, Tap Y was turned on to drain the water from the tank at a rate of 3 litres of water per minute. Both taps were turned off 8 minutes after Tap Y was turned on. What was the height of the water level in the tank when both taps were turned off?
After the 1st minute, amount of water in tank = 4L
For the next 8 minutes, amount of water entering tank = 8 X ( 4L - 3L ) = 8L
Total amount of water after both taps were turned off = 4L + 8L = 12L
Fraction of 12L / 60 L = 1/5
Hence height of water level = 1/5 of 30cm = 6cm
Thank you.