For this case we have the following equation: Q = Av Where the area is given by: A = pi * r ^ 2 A = pi * (d / 2) ^ 2 A = (pi / 4) * d ^ 2 Substituting we have: Q = ((pi / 4) * d ^ 2) v From here, we clear the diameter: d = root ((4 / pi) * (Q / v)) Substituting values we have: d = root ((4 / pi) * (50/600)) d = 0.36 feet Answer: The diameter of a pipe that allows a maximum flow of 50ft ^ 3 / min of water flowing at a velocity of 600ft / min is: d = 0.36 feet