Question

If C (20,r) = C[20,r-10), then C (18,r) is equal to-
(a)4896
(b)1632
(c)816
(d) none of these​

Answer 1

Hey mate

Hope it helps you

r+r-10=20
2r=30
r=15
18cr=18c15
18c15=18 factorial/15 factorial x 3 factorial
= 18 x 17 x 16/3 x 2
=816