Question

If ${}^n{C}_4=\frac{10}{6}{\times }^n{C}_2$, find the value of "n".

Answer 1

$\frac{{n_C}_4}{{n_C}_2}=\frac{10}{6}$

$\frac{n(n-1)(n-2)(n-3)\times 2}{n(n-1)\times 24}=\frac{5}{3}$

$(n-2)(n-3)=20$

$n=7$