Test Index

JAMB Mathematics 2020 Paper

© africaexams.com

Question : 35

Total: 40

Three consecutive terms of a geometric progression are give as n - 2, n and n + 3. Find the common ratio

$\frac{3}{2}$
$\frac{2}{3}$
$\frac{1}{2}$
$\frac{1}{4}$

Solution:

Concept:

In a geometric progression, the ratio of consecutive terms is constant.

So,

\frac{n}{n-2} = \frac{n+3}{n}

.

Explanation:

Set the ratios equal:

\frac{n}{n-2} = \frac{n+3}{n}

Cross-multiply:

n \cdot n = (n-2)(n+3)

n^2 = n^2 + n - 6

Subtract

n^2

from both sides:

0 = n - 6

n = 6

Now substitute

n = 6

into the first ratio:

\text{Common ratio} = \frac{6}{6-2} = \frac{6}{4} = \frac{3}{2}

Answer:

The common ratio is

\frac{3}{2}

, which is option A.

© africaexams.com

Go to Question:

Prev Question

Next Question