Math(more about probability)

2007-11-11 6:11 am

1.a number is picked at random from a set of numbers 2,3,4,5,6,7,8,9,10,11 and 12.If E is the event of picking an even number and F is the event of picking a multiple of 3,
(a)find P(E)
(b)find P(F)
(c)find P(E or F)

2.Two fair dice are tossed.
(a)Find the probability that the product is a prime number.
(b)Find the probability that the product is not a prime number.

回答 (1)

abaform

2007-11-11 6:45 am

✔ 最佳答案

1. Total number of choices
a) Even numbers in the set = {2, 4, 6, 8, 10, 12}
P(E) = 6/11
b) Numbers in the set which is a multiple of 3 = {3, 6, 9, 12}
P(F) = 4/11
c) Numbers in the set which is a multiple of 2 or 3 = {2, 3, 4, 6, 8, 9, 10, 12}
P(E or F) = 8/11
2a)
Total number of combinations = 6^2 = 36
Combinations for making the product a prime number = { (1, 2), (1, 3), (1, 5) }
P(product is a prime number) = 3/36 = 1/12
b) P(product is not a prime number) = 1 - 1/12 = 11/12

2007-11-10 22:47:48 補充：
Some modifications:2a) Combinations for making the product a prime number = { (1, 2), (1, 3), (1, 5), (2, 1), (3, 1), (5, 1) }P(product is a prime number) = 6/36 = 1/62b) P(product is not a prime number) = 1 - 1/6 = 5/6

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