Answer:
18
Explanation:
The height of the cone is 8, and the diameter is 3. This means that the radius is 3/2, or 1.5. We can plug everything into the formula (using 3 for pi):

We can cancel out the 3 from the numerator and the denominator, so we are left with 1.5^2 times 8. 1.5 squared is equal to 2.25, and 2.25 times 8 is equal to 18.