There are three urns. A, B, and C . Urn A contains 4 red balls and  3 black balls. Urn B contains 5 red balls and 4 black balls urn c contains 4 red and 4 black balls. New balls is drawn from each of these urns. What is the probability that 3 balls drawn consist of 2 red balls and a black ball?

Explanation

Let ,

`B_{1}`= draving black ball from win A

`R_{1}`= drawing red ball from wern A.

`P(B_{1})=frac{3}{4+3}=frac{3}{7}`
and `P(R_{1})=frac{4}{7}`

Siniliary, for won B and C.
`P(B_{2})=frac{4}{9} ` and `P(R_{2})=frac{5}{9}`

`P(B_{3})=frac{4}{8}=frac{1}{2}` and` P(R_{3})=frac{4}{8}=frac{1}{2}`

let P(s)=P (drawing two red ball and one black ball)

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