Solution:
Given:
Pipes A and B can fill an empty tank in 10 hours and x hours, respectively. Pipe C alone can empty a full tank In 9 hours.
When all three pipes are opened together, the tank is filled up completely in 18 hours.
Concept used:
Total work = Efficiency (Work done per hour) × Total time taken
Calculation:
Let the capacity of the tank be 90x units.
Pipe A fills the tank by = 90x/10 = 9x units a hour
Pipe B fills the tank by = 90x/x = 90 units a hour
Pipe C empties the tank by = 90x/9 = 10x units a hour
According to the question,
(9x + 90 - 10x) × 18 = 90x
⇒ 90 - x = 5x
⇒ 6x = 90
⇒ x = 15
∴ The value of x is 15.
