Let a_{1}, a_{2}, ......, a_{21} be an AP such that \\sum^{20}_{n=1} {1}/{a_n a_{n+1}}=\frac{4}{9}. If the sum of this AP is 189 , then a_{6} a_{16} is equal to [1 Sep 2021 Shift 2]

Sequences and Series Part 2

Section: Mathematics

Question : 63 of 100

Marks: +1, -0

Let a1,a2,......,a21 be an AP such that

n=1

anan+1

. If the sum of this AP is 189 , then a6a16 is equal to

[1 Sep 2021 Shift 2]

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