Question

Pipe A and B can fill a tank in $30$ and $15$ min, Pipe C empty $12$ liters of water in $1$min. If all of them are kept open when tank is full, tank can empty in $30$ min, What is the total capacity of tank?

• A. $90$ liters
• B. $135$ liters
• C. $180$ liters
• D. $360$ liters

Answer 1

The correct option is A $90$ liters

Work rate of A = 100/30 = 3.33 % per min
Work rate of B = 100/15 = 6.66 % per min
Work rate of (A + B) = 3.33 + 6.66 = 10 % per min
A and B together can fill the tank = 100/10 = 10 min
C emptied 12 liter per min. So, in 30 min C must has been emptied 30 *12 = 360 liter water.
In 30 min, A and B must fill 3 times the empty tank and as well as tank was fill initially.
So, capacity = 360 / 4 = 90 liter.