Question

what is the water flow ratein a 24 in. diamiter pipe in gpm. when the flow velocity is 3.0 ft per second

Answer 1

you want gal/s, so start converting, using what you have:

3.0 ft/s * 144pi ft^2 = 1357.17 ft^3/s
1gal = 231 in^3, so you have

1357.17 ft^3/s * 1728in^3/ft^3 * 1gal/231in^3 = 10152.32gal/s

Answer 2

oops. you want gal/min, so multiply by 60s/min