Mathematics · 2014
JEE Main · 9 April 2014, Shift 1 · Q70
If the sum 3/1^2+5/(1^2+2^2)+7/(1^2+2^2+3^2)+… ….+ upto 20 terms is equal to k/21, then k is equal to:
If the sum
$$\frac{3}{1^2}+\frac{5}{1^2+2^2}+\frac{7}{1^2+2^2+3^2}+\ldots \ldots .+ \text { upto }
$$
$\displaystyle 20$ terms is equal to $\displaystyle \frac{\mathrm{k}}{21}$, then k is equal to :
Official answer
(1)
$\displaystyle 120$
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JEE Main 2014 Mathematics question, with the answer from NTA’s final answer key. Where our answers come from.