Question

Tap A can fill a tank in 6 hours and tap B can empty the same tank in 10 hours. If both taps are opened together, then how much time (in hours) will be taken to fill the tank?

• A. 16
• B. 15
• C. 18
• D. 20

Answer 1

Answer:

B. 15

Solution: Given: Tap A can fill the tank in 6 hours and tap B can empty the same tank in 10 hours. Concept Used: If a pipe can fill or empty a tank in x hours then in 1 hour it can fill or empty 1/x part of the tank Calculation: Let, the total tank is 1 part Tap A can fill the tank in 6 hours That means in 6 hours tap A can fill 1 part of the tank ⇒ In 1 hour tap A can fill 1/6 part of the tank Tap B can empty the tank in 10 hours That means in 10 hours tap B can empty 1 part of the tank ⇒ In 1 hour tap B can empty 1/10 part of the tank In 1 hour part of the tank will be filled when both taps are opened together is (1/6 – 1/10) ⇒ (5 - 3)/30 ⇒ 2/30 ⇒ 1/15 To fill the tank time taken is 1/(1/15) hours ⇒ 15 hours ∴ If both taps are opened together the tank will be filled in 15 hours.