Hemispherical bowl Volume question

[lovemake1]

Homework Statement

Question Reads...
A hemispherical bowl 60cm in diameter is filled to within 5 cm of the top. Thirty minutes after the party starts, there are only 5cm of punch left at the bottom of th bowl.

a) how much punch was there at the beginning of the party?
b) How much punch was consumed

Homework Equations

V of hemispherical bowl = 2/3(pi)(r)^3
r = 30
h = 30

The Attempt at a Solution

since this is a hemisphere we would have to find a volume using r interms of h right?
and by using h = 25 since its 30-5.

How should i begin? any advice appreciated.

 

[LCKurtz]

I would draw a semicircle, shading the cross section of the part that was used and do a volume by revolution.