Question: If $nC_{r - 1} = 36,^{n}C_{r} = 84$ and $nC_{r + 1} = 126$ then the value of r is...

Question

If $nC_{r - 1} = 36,^{n}C_{r} = 84$ and $nC_{r + 1} = 126$ then the value of r is

Answer 1

Here $\frac{nC_{r - 1}}{nC_{r}} = \frac{36}{84}$ and $\frac{nC_{r}}{nC_{r + 1}} = \frac{84}{126}$

$3n - 10r = - 3$ and $4n - 10r = 6$ ; on solving we get $n = 9$ and $r = 3$ .

Question: If \(nC_{r - 1} = 36,^{n}C_{r} = 84\) and \(nC_{r + 1} = 126\) then the value of r is...