If $^{n}P{r} = 840$ and $^{n}C{r} = 35$, find the value of $r$.

Question

Accepted Answer

We know that $^{n}P{r} = r! 	imes ^{n}C{r}$. Substituting the values, $840 = r! 	imes 35 \implies r! = \frac{840}{35} = 24$. Since $4! = 24$, $r = 4$. Thus, option D is correct.

Permutations and Combinations

❓ Sibling Questions in this Chapter