A tank is 2/5 full. Pipe A can fill the whole tank in 10 minutes and pipe B can empty it in 6 minutes. If both are opened, how long will the tank take to empty?
Correct answer D. 6 minutes
Explanation
Net emptying rate = 1/6 − 1/10 = 1/15 per minute. Emptying 2/5 of the tank takes 2/5 × 15 = 6 minutes.
Answer checked How we write and check questions
Discussion