Let a1,a2,a3⋯,a21 be an AP such that 20∑n=11anan+1=49 If the sum o – InterviewSolution

1.	Let a1,a2,a3⋯,a21 be an AP such that 20∑n=11anan+1=49 If the sum of this AP is 189, then a6a16 is equal to:
Answer» Let $a_{1}, a_{2}, a_{3} \dots, a_{21}$ be an $A P$ such that $20 \sum n = 1 \frac{1}{a_{n} a_{n + 1}} = \frac{4}{9}$ If the sum of this $A P$ is $189$ , then $a_{6} a_{16}$ is equal to:

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