Triple Integrals (volumes)

[Bob Ho]

1. The problem statement, all variables and given/known data
A solid is definited by the inequalities 0\leqx\leq1, 0\leqy\leq1, and 0\leqz\leqx2+y2. The temperature of the solid is given by the function T=25-3z. Find the average temperature of the solid.


3. The attempt at a solution

I solved the integral, however I could not figure out how to determine what to do to find the average temperature value. In the answers i was given. They have no explanation, just the volume of solid above the inequalities is (!) 2/3.
So they therefore times the integral by 3/2.

Can someone please explain how this idea works? Thanks

[gabbagabbahey]

The average value of any function f(x,y,z) over some volume \mathcal{V} is, by definition;

\langle f \rangle \equiv \frac{\int_{\mathcal{V}}f dV}{\int_{\mathcal{V}} dV}

...apply that to T(z)