The flow of water moves through the pressure pipe with

The flow of water moves through the pressure pipe with a diameter of 40 mm with a flow rate of Q, l / s. Determine the average flow rate when switching to a diameter half as small.
It is set: the initial diameter of the pipeline d1 = 40 mm = 0.04 m; the final diameter of the pipeline d2 = 20 mm = 0.02m; Q = 0.2 l / s = 0.2 * 10-3 m3 / s.
Determine: average flow rate vav.