Let a₁, a₂,..........., a₂₁ be an AP such that Σ n = 1 ²⁰ 1 a n a n + 1 = 4/9. If the sum of this AP is 189, then a₆a₁₆ is equal to:

Sequence and Series: JEE Main 2021 Mathematics question

JEE Main 2021 · 1 Sep, Evening shift · Q5223

JEE Main 20211 Sep, Evening shiftMathematicsMediumSequence and Series179× since 2002

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

\sum\limits_{n = 1}^{20} {{1 \over {{a_n}{a_{n + 1}}}} = {4 \over 9}}

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

JEE Main 2021 · 1 Sep, Evening shift · Q5223

JEE Main 20211 Sep, Evening shiftMathematicsMediumSequence and Series179× since 2002

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

\sum\limits_{n = 1}^{20} {{1 \over {{a_n}{a_{n + 1}}}} = {4 \over 9}}

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