Question
Evaluate: $\frac{n !}{r !(n-r) !}$ for : $\mathrm{n}=8, \mathrm{r}=6$

Answer

$
\begin{aligned}
& n=8, r=6 \\
& \therefore \quad \frac{n !}{r !(n-r) !}=\frac{8 !}{6 !(8-6) !} \\
& =\frac{8 \times 7 \times 6 !}{6 ! 2 !} \\
& =\frac{8 \times 7}{2 !} \\
& =\frac{8 \times 7}{1 \times 2}=28 \\
&
\end{aligned}
$

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