Each revolution of the red needle corresponds to 1 cubic foot of water. The dial is divided into tenths of cubic feet.
Use a stopwatch to time how long it takes for the red needle to move a tenth of a cubic foot.
Assume it takes 2 minutes for the red needle to move from 0.4 to 0.5 on the dial, which would correspond to 0.1 cubic foot of water flowing in 2 minutes. To calculate how much water is flowing in an hour (i.e. in 60 minutes):