i don’t know it is right or not

3 x 5 = 15 

4 x 7 = 28

5 x 9 = 45 

12 x11 = 120

 

I need to know if I did this right Please let me know

This was part of a test I took inclass and I bombed it... I need to know the right way to do it.Thank you.

Find the volume of the frustum of a right circular cone withheight h=7, lower base radius R=2 and top radius r=4

I was provided an anser of (196/3) * π but do not know how toderive it.