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JEE MATHEMATICS MCQ: COMBINATIONS

1 Easy

1 of 1

Application +4 | -1

If

{a_n} = \sum \limits_{r = 0}^m \frac{1}{{{\;^n}{C_r}}},\;{\text{then}}\;\sum \limits_{r = 0}^n \frac{r}{{{\;^n}{C_r}}}

equals

View answer and explanation

Correct option: C

\frac{1}{2}n{a_n}

Option C (

\frac{1}{2}

n{a_n}) is correct because by using the property of combinations and summing the series in reverse, we can find the required sum.

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