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#1
07-27-2012, 10:53 AM
 samzhang2003 CAS Join Date: Jun 2012 Location: New Jersey Studying for Exam C College: University of Rochester Posts: 9
TIA practice exam 4, Q.9

An insurance company categorizes its customers as low risk, medium risk, and high risk. Suppose that
20% are low risk, 50% are medium risk, and 30% are high risk. If 5 customers are chosen at random,
what is the probability that exactly twice as many of them are low risk as high risk given that at least
one customer chosen is high risk?

I'm having trouble to understand the highlight sentence.
Does it mean 2L= H or 2H=L?

Originally I thought it's 2L=H, then I saw "twice as many girls as boys" means 2B=G. So I'm confused now.

Thanks
#2
07-27-2012, 11:48 AM
 KDB10 Member SOA Join Date: Jun 2012 Posts: 46

If 5 are high risk, and twice as many are low risk as high risk, then ten (2*5) are low risk.

Therefore, 2H = L (or substituting numbers, 2*5 = 10)

Same with your girls & boys deal. If there is one boy, and there are twice as many girls as boys, there are 2*1 = 2 girls, or 2B = G
#3
07-27-2012, 04:27 PM
 ronaldy27 Member CAS SOA Join Date: Jan 2012 Location: 9th dimension Studying for C and MLC College: SUNY Binghamton Alumni Posts: 550

Quote:
 Originally Posted by samzhang2003 An insurance company categorizes its customers as low risk, medium risk, and high risk. Suppose that 20% are low risk, 50% are medium risk, and 30% are high risk. If 5 customers are chosen at random, what is the probability that exactly twice as many of them are low risk as high risk given that at least one customer chosen is high risk? I'm having trouble to understand the highlight sentence. Does it mean 2L= H or 2H=L? Originally I thought it's 2L=H, then I saw "twice as many girls as boys" means 2B=G. So I'm confused now. Thanks
Remember, you are trying to set them equal.
So if you look at the statement, "exactly twice as many of them are low risk as high risk," then to make them equal you have to have 2(H)=(L)
__________________

#4
07-29-2012, 01:23 PM
 samzhang2003 CAS Join Date: Jun 2012 Location: New Jersey Studying for Exam C College: University of Rochester Posts: 9

Thanks for the explanation.

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