More about probability

myteapot172000

2011-04-23 6:50 am

1.
There are 10 chips marked with 1 to 10 in bag.Two chips are taken in sucession with replacement.What is the probability that the number on the first chip is greater than that on the second one.

2.
There are 8 boxes of which 2 contain sweets.If a boy opens the boxes at radom one by one without repetition,what is the probability that he can find some sweets within 2 trials?

3.
A fly lands on a circular cake of diameter 20cm.What is the probability that is at least 6 m from the certre of the cake?

回答 (1)

myisland8132

2011-04-23 7:20 am

✔ 最佳答案

1 no. of ways = 10*10 = 100

Among these choices. 10s' are equal (1,1).(2,2) ...(10,10) 45s' are first one greater than second one. Probability = 45/100 = 9/20

2 1 - P(no sweet)

= 1 - C(6,2)/C(8,2)

= 1 - 15/28

= 13/28

3 Probability = (10^2 - 6^2)/10^2 = 16/25

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