agdimple333 wrote:

A certain business school has 500 students, and the law school at the same university has 800 students. Among these students, there are 30 sibling pairs consisting of 1 business student and 1 law student. If 1 student is selected at random from both schools, what is the probability that a sibling pair is selected?

3/40,000

3/20,000

3/4,000

9/400

6/130

In the above Q, what the green color text means? i think it means 2 students (pair) to be selected from the gang since it is mentioned in the red that sibling pair is selected but i just thought that green text is missing 'each'.

Good point agdimple333:

I prefer the wordings of the following link:

probability-57997.htmlThe use of word "both" and "pair" indeed creates some ambiguity as to whether we need to choose 2 students from each class OR 1 student from both classes combined.

Let's see using both scenarios:

If 2 students, 1 from each class, need to be selected.

P(Pick Sibling Pair)=(30/500)*(1/800)=30/400000= 3/40000

If just 1 student needs to be selected,

P(Pick from Sibling Pairs)=(30+30)/(500+800)=60/1300=6/130

_________________

~fluke

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