Hi aspirant

Using the equation of continuity, we can solve this problem

                                              A1*V1=A2*V2

A= Area of the pipe; Πr2

V= Velocity of water

x= rate of flow in a reduced radius

Applying the equation,

                πr 12  * V1= πr22 *V2

So,            64*2 = 16*X

                 64*2/16=X

                  X= 8m/s.