Question

A drain pipe can drain a tank in 12 hours, and a fill pipe can fill the same tank in 6 hours. A total of n pipes, which include a few fill pipes and the remaining drain pipes can fill the entire tank in 2 hours. How many of the following values could n have in this case? a. 24 b. 16 c. 33 d. 13 e. 9 f. 8

• A. 12
• B. 13
• C. 5
• D. 3
• E. 2

Hint:

In pipe problems, express rates as fractions of tank per hour. For fill pipes, rate is positive; for drain pipes, rate is negative.

Answer 1

The Correct Option is D