SOLUTION: https://vle.mathswatch.co.uk/images/questions/question2752.png please help

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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