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13.Statistics
medium
જો $1,2,3, \ldots ., n$, (જ્યાં $n$ અયુગ્મ છે.) નો મધ્યકથી સરેરાશ વિચલન $\frac{5(n+1)}{n}$ હોય, તો $n$ = ............
A
$20$
B
$25$
C
$23$
D
$21$
(JEE MAIN-2022)
Solution
Mean deviation about mean of first $n$ natural numbers is $\frac{ n ^{2}-1}{4 n }$
$\therefore n =21$
Standard 11
Mathematics