SOLUTION: Two representatives are chosen from random from a group of 80 students that has 40 boys and 40 girls. What is the probability that both representatives are girls.
a. 20/79
b.
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a. 20/79
b.
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Question 611373: Two representatives are chosen from random from a group of 80 students that has 40 boys and 40 girls. What is the probability that both representatives are girls.
a. 20/79
b. 1/4
c. 39/158
d. 39/160
I think the answer is b is that correct? Answer by solver91311(24713) (Show Source):
Answer b would be correct if you put the first one you picked back into the mix and then picked the second one allowing for the possibility that both choices would be the same person. Since that is a ludicrous idea for choosing two representatives, we have to assume non-replacement, and therefore dependent probability.
The probability of the first selection being a girl is indeed 1/2, but once a girl has been selected for the first representative, there are now only 39 girls left in a total population of 79 students. Hence, the probability of picking a girl on the second draw is reduced to 39/79. The probablity of both events, i.e. girl on first draw and girl on second draw is the product of the two probabilities, 1/2 times 39/79. You can do your own arithmetic.
John
My calculator said it, I believe it, that settles it
