Blood types A, B, O, and AB have percentages 40%, 20%, 30% and 10%. If two individuals are chosen at random, assuming independence, how do you find probability that one is blood type A and the other is type O?

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Answer 1 · 2016-03-27T13:51:13

Let's first translate percentages into fractions, meaning #100%harr1.00#

Then #p(A)=0.40,p(B)=0.20, p(O)=0.30,p(AB)=0.10)#
Since they're independent , we may multiply :

The probability of taking an #A# and then an #O# is:
#p(A,O)=p(A)xxp(O)=0.4xx0.3=0.12#

The same goes for the other way aound:
#p(O,A)=p(O)xxp(A)=0.3xx0.4=0.12#

So the total probability (since it's either O-A or A-O we may add )

#p(O^^A)=p(A,O)+p(O,A)=0.12+0.12=0.24#

Which translates to #p(O^^A)=24%#