The sum of the first three terms of a geometric progression is half its sum to infinity. Find the positive common ratio of the progression.

Question 1 Report

\frac{1}{4}

\sqrt{\frac{3}{2}}

\frac{1}{\sqrt{3}}

\frac{1}{\sqrt{2}}

Answer Details

Let the G.P be a, ar, ar2, S3 = $\frac{1}{2}$ S
a + ar + ar2 = $\frac{1}{2}$ ( $\frac{a}{1 - r}$ )
2(1 + r + r)(r - 1) = 1
= 2r3 = 3
= r3 = $\frac{3}{2}$
r( $\frac{3}{2}$ ) $\frac{1}{3}$ = $\sqrt{\frac{3}{2}}$

Read lesson note on Sequence And Series (WAEC)

Sequence And Series

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