If $C (28, 2 r) = C (28, 2 r - 4)$ , then what is $r$ equal to?

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Solution

The correct option is B $8$
We know that, $^{n} C_{k} =^{n} C_{n - k}$
Here $n = 28, k = 2 r$
$\Rightarrow n - k = 2 r - 4$ ..... $[∵^{28} C_{2 r} =^{28} C_{2 r - 4}]$
$\Rightarrow 28 - 2 r = 2 r - 4$
$\Rightarrow 4 r = 32$
$\Rightarrow r = 8$
Hence, $r = 8$

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If C(28,2r)=C(28,2r−4), then what is r equal to?

The correct option is B 8We know that, nCk=nCn−kHere n=28,k=2r ⇒n−k=2r−4 ..... [∵28C2r=28C2r−4]⇒28−2r=2r−4⇒4r=32⇒r=8Hence, r=8

If $C (28, 2 r) = C (28, 2 r - 4)$ , then what is $r$ equal to?

The correct option is B $8$
We know that, $^{n} C_{k} =^{n} C_{n - k}$
Here $n = 28, k = 2 r$
$\Rightarrow n - k = 2 r - 4$ ..... $[∵^{28} C_{2 r} =^{28} C_{2 r - 4}]$
$\Rightarrow 28 - 2 r = 2 r - 4$
$\Rightarrow 4 r = 32$
$\Rightarrow r = 8$
Hence, $r = 8$