If 28 C 2r : 24 C 2r – 4 : 225 : 11, find r.

Question

Philoid · Accepted Answer

Given:

⇒

We know that

And also n! = n(n – 1)(n – 2)…………2.1

⇒

⇒ (2r)(2r – 1)(2r – 2)(2r – 3) = 11 × 12 × 13 × 14

Equating the corresponding terms on both sides we get,

⇒ 2r = 14

⇒

⇒ r = 7

∴ The value of r is 7.

If 28C2r : 24C2r – 4 : 225 : 11, find r.