Question:
If nC12 = nC6, then nC2 = ____________.
Solution:
Given nC12 = nC6
Using nCr = nCn−r
⇒ n − 6 = 12
n = 18
$\Rightarrow^{18} C_{2}=\frac{18 \times 17 \times 16 !}{16 ! \times 2}$
$=9 \times 17$
i.e 18C2 = 153
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