Probability?

2016-02-17 5:17 pm

1.The probability for Steven to hit the basket in a basketball shot is 0.4. If Steven makes three basketball shots find the probability of hitting two shots.

2. There are 5 res balls , 3 green balls amd 2 white balls in a bag . If two balls are drawn at random one by one with replacement,fins the probability that
(a) one red ball and one white ball are draen
(b) the two balls are same in colour

3. On average, David can answer correctly 2 questions out of 5,and Amy can answer correctly 1 out of 3 . If they attempt the same question separately , whats the probability of having the question solved?

回答 (1)

未命名

2016-02-18 5:50 am

ans1 : Steven makes three basketball shots with hitting two, which means one is missed, on the other hand, the missed ball could be the first,second, third shot, thus, the probability is (2/5)^2*(3/5)*3.

ans2 : i'm not quite sure the meaning of "with replacement". Does it mean right put back the ball drawn from the bag after the first draw?

ans3 : we first consider the probability of they both unsolve the question, cause if we consider the situation in a positive practice, that is, the question is solved no matter by whom, it will be a little complicated to do so, since the solver could be David, Amy, or both of them. therefore, (1-(2/5))*(1-(1/3)) is the probability of the problem unsolved, since it requires they both fail to answer correctly, so, the probablilty of the question is solved(no matter by whom) is 1-(1-(2/5))*(1-(1/3)).

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