The first term of a geometric progression is twice its common ratio. Find the sum of the first two terms of the G.P if its sum to infinity is 8.

Assessment: JAMB UTME - Mathematics - 1999 Subject: General Mathematics

Question 1 Report

The first term of a geometric progression is twice its common ratio. Find the sum of the first two terms of the G.P if its sum to infinity is 8.
Answer Details
Le the common ratio be r so that the first term is 2r.

Sum, s = a/(1-r)
ie. 8 = 2r/(1-r)

8(1-r) = 2r, r = 8/5.

Sn = a(1-rn)/(1-r)
Solve further to get 72/25

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