Hi Please help in this question,
A certain junior class has 1000 students and a certain senior class has 800 students. Among these students 60 sibling pairs, each consisting of 1 junior and 1 senior. If 1 student to be selected from each class what is the probability that the 2 students selected will be a sibling pair?
a) 3/40000
b)1/3600
c) 9/2000
d) 1/60
e) 1/15
Regards,
Please Help-Probability
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- cubicle_bound_misfit
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i think the answer is 9/2000.
here it goes..
60 siblings means there are 120 students. therefore..
probability of choosing 1 senior out of 1000 students who is a sibling is
60C1/1000C1.....illy
junior who is a sibling is also 60C1/1000C1
therefore the probability is 60/1000 * 60/800
which is 9/2000.
here it goes..
60 siblings means there are 120 students. therefore..
probability of choosing 1 senior out of 1000 students who is a sibling is
60C1/1000C1.....illy
junior who is a sibling is also 60C1/1000C1
therefore the probability is 60/1000 * 60/800
which is 9/2000.
- cubicle_bound_misfit
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Thanks.
That's what I did my friend.
But the OA is A? :!:
Can someone please explain why?
Regards,
That's what I did my friend.
But the OA is A? :!:
Can someone please explain why?
Regards,
Cubicle Bound Misfit
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i think then the only way it can be solved is ,,,,
x = prob of choosing a senior who has a sibling
y = prob of choosing senior's sibling from junior class
Z = prob of having chosen a sibling pair
Z = x.y
= 60/800 . 1/1000
= 3/40000
seems very simple to be correct.
x = prob of choosing a senior who has a sibling
y = prob of choosing senior's sibling from junior class
Z = prob of having chosen a sibling pair
Z = x.y
= 60/800 . 1/1000
= 3/40000
seems very simple to be correct.