Probability

[kluevehe]

There is a total number of 120 marbels in a box, each of which is red, green, blue or while. If one marble is drawn from the box at random, the probalilty that will be white is 1/4 and the prob. that it will be green is 1/3. What is the prob. that the marble will be either red or green?



Official Answer: 5/12

[krovvidy]

There is a total number of 120 marbels in a box, each of which is red, green, blue or while. If one marble is drawn from the box at random, the probalilty that will be white is 1/4 and the prob. that it will be green is 1/3. What is the prob. that the marble will be either red or green?

Official Answer: 5/12

I think the qn has a typo ... probability of blue marble should've been given instead of green one ... Anyways, assuming that P(blue) = 1/3, here's the solution ...

P(red) + P(green) = [1 - P(green) - P(white) - P(blue)] + P(green)
i.e., 1 - P(white) - P(blue)
i.e., 1 - 1/4 - 1/3
i.e., 1- 7/12
i.e., 5/12