Dalam 1 kotak pensil terdapat 20 pensil warna dimana 8 warna merah, 7 warba putih dan sisanya warna hitam. Jika diambil 4 pensil dari kotak tersebut. Berapa ban

8 merah
7 putih
5 hitam
total 20

a. n(a)
8c2 × 7c1 × 5c1 = 28 × 7 × 5 =980
8c2 × 7c2 = 28 × 21 = 588
8c2 × 5c2 = 28 × 10 = 280
8c3 × 7c1 = 56 × 7 = 392
8c3 × 5c1 = 56 × 5 = 280
8c4 = 70

= 980 + 588 + 280 + 392 + 280 + 70
= 2590

n(s)
20C4 = 4845

= n (a) / n (s)
= 2590 / 4845
= 518 / 969

b. n (a)
5c1 × 7c2 × 8c1 = 5 × 21 × 8 = 840
5c1 × 7c1 × 8c2 = 5 × 7 × 28 = 980
5c1 × 7c3 = 5 × 35 = 175
5c1 × 8c3 = 5 × 56 = 280
5c2 × 7c1 × 8c1 = 10 × 7 × 8 = 560
5c2 × 7c2 = 10 × 21 = 210
5c2 × 8c2 = 10 × 28 = 280
5c3 × 7c1 = 10 × 7 = 70
5c3 × 8c1 = 10 × 8 = 80

840 + 980 + 175 + 280 + 560 + 210 + 280 + 70 + 80 = 3475

= n(a) / n(s)
= 3475/4845
= 695/696