JEE Main 2022 · 27 Jul · Shift 2 · Mathematics Q7

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MathematicsSingle correct+4 / -1Question 7 of 90

Let the sum of an infinite G.P., whose first term is $a$ and the common ratio is $r$ , be 5. Let the sum of its first five terms be $\dfrac{98}{25}$ . Then the sum of the first 21 terms of an AP, whose first term is $10ar$ , $n^{\text{th}}$ term is $a_n$ and the common difference is $10ar^2$ , is equal to :

21a_{11}

22a_{11}

15a_{16}

14a_{16}

Answer and worked solution

Official answer: A

Middle term. An AP with 21 terms has $S_{21}=21\times$ its 11th term, whatever $a$ and $r$ are.

(A)

Topics:Arithmetic progression Geometric progression

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JEE Main 2022 · 27 Jul · Shift 2, Mathematics question 7