NDA 2023 Maths · Mathematics · Sequences and Series · easy

In a geometric progression the third term is 12 and the sixth term is 96. The first term is

Single correct option

In a geometric progression the third term is

12

and the sixth term is

96

. The first term is

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Answer: (B) $3$

Dividing,

\dfrac{ar^5}{ar^2}=r^3=\dfrac{96}{12}=8

, so

r=2

. Then

ar^2=12

gives

4a=12

and

a=3

. A frequent error is to take

r=8

(the ratio of three steps) and conclude

a=12/64

Original question written in the NDA 2023 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake