Question

The 5th term in a geometric sequence is 162. The 2nd term is 6, The sum of the 1st 5 terms is.

Answer 1

Explanation:

t2 = a*r

t2 = 6

t5 = a*r^4

t5 = 162

162/6 = ar^4 / ar

r^3 = 27

r = 3

6 = a*3

2 = a

Sum = a(r^n - 1)

=======

r - 1

n = 5

a = 2

r = 3

Sum = 2(3^5 - 1)

=======

2

Sum = 242