Question

There is a bag filled with 5 blue, 6 red and 2 green marbles. A marble is taken at random from the bag, the colour is noted and then it is replaced. Another marble is taken at random. What is the probability of exactly 1 red?

Answer 1

6/13

Explanation:

If the first marble drawn is replaced (and the bag of marbles is shaken so as to be returned to a random distribution of the marbles), then the probability of exactly 1 red is

number of red marbles

-------------------------------------- = 6/13

total number of marbles