UPSC NDA I 2021 Mathematics Solved Paper

Concept
Let us consider sequence a1,a2,a3...an is an G.P.
Common ratio =r=‌

a2

a1

=‌

a3

a2

=‌

an

an−1

Calculation:
Let a be the 3rd term of the G.P series,
So, we can write the five terms as,
‌

a

r2

,‌

a

r

,a,ar,ar2
So, the product of the five terms =a5
Since a=3, the product of the first five terms =35=243