Page 80 - Probability Demystified

CHAPTER 4 The Multiplication Rules 69

3. There are 2 black aces and 26 black cards; hence, P(ace|black
card) ¼ 2 or 1 or
26 13
P(ace and black card)
P(ace black cardÞ¼
j
P(black card)
2
52
¼
26
52
2 26
¼
52 52
2 1 52 1
¼
52 1 26 13
1
¼
13

4. P (Sand CrabjRainbow Gardens)
P(Sand Crab and Rainbow Gardens)
¼
P(Rainbow Gardens)
0:20
¼ ¼ 0:25
0:80

5. There is one way to get 3 twos—(2, 2, 2) and there are 10 ways to get
a sum of six—(2, 2, 2), (3, 2, 1), (1, 2, 3), (2, 1, 3), (2, 3, 1), (3, 1, 2),
(1, 3, 2), (4, 1, 1), (1, 4, 1,) and (1, 1, 4). Hence,
P(3 twos and sum of 6)
P(3 twosjsum of 6) ¼
P(sum of 6)
1
36
¼
10
36
1 10
¼
36 36
1 36 1
¼
36 1 10
1
¼
10