Permutations and Combination — Maths STD 11 Science — Question

$\begin{aligned} \therefore \quad \frac{n !}{r !(n-r) !} & =\frac{15 !}{8 !(15-8) !} \\ & =\frac{15 \times 14 \times 13 \times 12 \times 11 \times 10 \times 9 \times 8 !}{8 ! \times 7 !} \\ & =\frac{15 \times 14 \times 13 \times 12 \times 11 \times 10 \times 9}{7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1} \\ & =5 \times 13 \times 11 \times 9 \\ & =6435\end{aligned}$