Question

Two pipes A and B can fill a tank in 12 hours and 18 hours, respectively. Both pipes are opened simultaneously. In how much time will the empty tank be filled completely ?

• A. 10 hours 24 minutes
• B. 9 hours 30 minute
• C. 8 hours
• D. 7 hours 12 minutes

Answer 1

Answer:

D. 7 hours 12 minutes

Solution: Given: Time is taken by A to fill the tank = 12 hrs Time is taken by B to fill the tank = 18 hrs Concept used: Total time = Volume/Volume filled in 1 hour Calculation: Volume filled by A in 1 hr = 1/12 Volume filled by B in 1 hr = 1/18 Volume filled by both A and B in 1 hr = 1/12 + 1/18 ⇒ Volume filled by both A + B in 1 hr = (3 + 2)/36 ⇒ Volume filled by both (A + B) in 1 hr = 5/36 Total Time to fill the tank = (Total volume of the tank)/(Volume filled by both (A + B) in 1 hr) ⇒ Total Time to fill the tank = 1/(5/36) ⇒ Total Time to fill the tank = 36/5 hr ⇒ Total Time to fill the tank = 7 hours 12 minutes ∴ The total time to the filled the empty tank is 7 hours 12 minutes.