Sebuah kantong plastik berisi 8 kelereng merah dan 10 kelereng putih. Jika diambil 2 kelereng sekaligus secara acak,maka peluang yang terambil 2 kelereng merah

= C8,2/C18,2
= 8!/2!(8-2)! / 18!/2!(18-2)!
= 8!7!6!/2×1×6! / 18×17×16!/2×1×16!
= 8x7/2×1 / 18×17/2×1
= (56/2) / (306/2)
= 28/153

8 merah , 10 putih = 18 kelereng

Diambil 2 kelereng sekaligus
n(S) = 18C2 = 18!/(18 - 2)!2! = (18.17.16!)/(16!2.1) = 9 . 17 = 153

Terambil 2 kelereng merah
n(A) = 8C2 = 8!/(8 - 2)!2! = (8.7.6!)/(6!.2.1) = 4 . 7 = 28

Peluang = P(A) = 28/153