Question

The common ratio of a geometric series is 1/4 and the sum of the first 4 terms is 170

what is the first term of the series? its 128

Answer 1

128

Explanation:

As common ratio is 1/4 ; let the first four terms of the geometric series be :

x , 1 / 4 .x , (1 / 4)2 .x , (1 / 4)3 .x or

x , x / 4 , x / 16 and x / 64

Now there sum is 170 , hence

x + x / 4 + x / 16 + x / 64 = 170 or

(64a + 16a + 4a + a ) / 64 = 170 or

85a / 64 = 170

a = 128

Hence first first term of the series is

128

Answer 2

The first term is 128

Step-by-step explanation:please see attachment for explanation