Question

4meisu
The first term of a geometry sequence is 200 and the sum of the first 4 terms is 3248. What is the common ratio, and find the 10th term.

Answer 1

first term a1 = 200
sum of first four term = 3248
which means
a1 * r^3 = 3248
200 * r^3 = 3248
r^3 = 3248/200
r^3 = 406/25
r = 2.532

hence the 10th term will be
a10 = a1 * r^9
= 200 * (r^3)^3
= 200 * (406/25)^3
= 856619.7

Answer 2

200 * r^4 - 1
------ = 3248
r - 1