For a geometric sequence with common ratio

, we have

that is, the

-th term in the sequence is the product of the previous term and the common ratio

. So

Then the sum of the first 7 terms is


Notice that

so we can subtract this modified sum from

to get

We're told that

and

, so the sum of the first 7 terms is
7056. 1008 x 7 = 7056. 7056 / 441 = 16
30?
30pi = 2pi r
30pi / 2pi = 15
15 = r
double the radius to get the diameter
15)2 =30
(4x2) + (3x1)=11
I think that's right, can you have a plus sign