If Σ i = 1 ²⁰ ((²⁰C i - 1)/(²⁰C i + ²⁰C i - 1)) ³ = k/21 then k is equal to

Binomial Theorem and Its Simple Applications: JEE Main 2019 Mathematics question

JEE Main 2019 · 10 Jan, Morning shift · Q2986

JEE Main 201910 Jan, Morning shiftMathematicsMediumBinomial Theorem and Its Simple Applications131× since 2002

{\sum\limits_{i = 1}^{20} {\left( {{{{}^{20}{C_{i - 1}}} \over {{}^{20}{C_i} + {}^{20}{C_{i - 1}}}}} \right)} ^3} = {k \over {21}}

then k is equal to

JEE Main 2019 · 10 Jan, Morning shift · Q2986

JEE Main 201910 Jan, Morning shiftMathematicsMediumBinomial Theorem and Its Simple Applications131× since 2002

{\sum\limits_{i = 1}^{20} {\left( {{{{}^{20}{C_{i - 1}}} \over {{}^{20}{C_i} + {}^{20}{C_{i - 1}}}}} \right)} ^3} = {k \over {21}}

then k is equal to