Question

A cistern, when full is emptied by a waste pipe in 30 min., but if a tap (filling source) is opened, it takes 40 min, to empty the cistern. How long the cistern will take to become full when both the pipes are working together?

Answer 1

Answer:

120 Mins

Step-by-step explanation:

Correct Question :

A cistern, when full is emptied by a waste pipe in 30 min., but if a tap (filling source) is opened, it takes 40 min, to empty the cistern

How long the cistern will take to become full when filling source is working only

Let say pipe Take  A min to fill the tank

Tank filled in 1 min  = 1/A

Tank emptied in 1 min = 1/30

Together Tank Emptied = 1/30 - 1/A  = 1/40

=> 1/A = 1/30 - 1/40

=> 1/A = (4 - 3)/120

=> A = 120

pipe fill fill the tank in 120 mins