Question

If a 2-inch pipe will fill a tank in 6 hours, how long will it require for a 3-inch pipe to fill it?

Answer 1

"2-inch" and "3-inch" presumably refer to the diameter of the pipe, so the 3-inch pipe has (3/2)^2 or 2.25 times the cross-sectional area. Which means it can deliver fluid at 2.25 times the rate.

6 hours / 2.25 = 2 2/3 hours (2 hours and 40 minutes)