Question

Two pipes A and B can fill a tank in 40 and 48 minutes respectively, and a waste pipe can empty 5 gallons per minute. All the three pipes working together can fill the tank in 30 minutes. The capacity of the tank is:
1. 450 gallons
2. 500 gallons
3. 400 gallons
4. 480 gallons

Answer 1

Correct Answer - Option 3 : 400 gallons

Given:

A and B can fill a tank = 40 min and 48 min

Waste pipe can empty the tank = 5 gallons per minute

All the three pipes working together can fill the tank = 30 min

Calculation:

Work done by the waste pipe in 1 min

⇒ 1/30 – (1/40 + 1/48)

⇒ 1/30 – (6 + 5)/240

⇒ 1/30 – 11/240

⇒ (8 – 11)/240

⇒ -3/240

⇒ -1/80

Volume of 1/80 part = 5 gallons

Volume of the whole gallon = 80 × 5

⇒ 400 gallons

∴ The capacity of the gallons is 400