First slide

Combinations

Question

A student is allowed to select at most ‘n’ books from a collection of $(2n + 1)$ books. If the total no. of ways in which he can select one or more books is 63, then n is

Easy

A

1
B

2
C

3
D

4

Solution

$2^{2 n} - 1 = 63$
$\Rightarrow 2^{2 n} = 64 \Rightarrow 2 n = 6$

$\Rightarrow n = 3$

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