Someone pleeaaasseee ! whoever answers the most correctly and gives an explanation gets

Problem 6:

Volume is 5 pi cm^3, and height is 15 cm.

                                                                        5 pi cm^3
Then the area of the (round) base must be         
                                                                         15 cm

or A = (pi/3) cm^2.

We want the radius of the base.  The formula for that is pi * r^2.

Equate    pi * r^2 and (pi/3) cm^2.  "pi" cancels.  Then r^2 = 1/3.

The radius of the base is the sqrt of 1/3, which is approx. 0.58 cm.