Question 1118103: https://vle.mathswatch.co.uk/images/questions/question2752.png
please help
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! i believe your answer will be as follows:
you have 1 blue and the rest red out of n.
that means 1 blue and n-1 red.
the probability of drawing 1 blue and 1 red is therefore:
c(2,1) * 1/n * (n-1/(n-1) = 2/n.
if the probability is .125, then 2/n = .125.
solve for n to get n = 16.
note that .125 is equal to 1/8.
you can confirm this is true by letting n = 16.
that gives you 1 blue and 15 red.
you can determine the probability in 2 ways that i know of.
first is (c(2,1) * 1/16 * 15/15 = 2 * 1/16 = 2/16 = 1/8.
second is (c(1,1) * c(15,1) / c(16,2).
this becomes (1 * 15) / (16 * 15 / 2).
this becomes (15 * 2) / (16 * 15)
this results in 2/16 which becomes 1/8.
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