Question

There is a bag filled with 4 blue, 3 red and 5 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 getting exactly 1 blue?

Answer 1

Answer:

The probability of selecting a red marble the first time is 1 by 3 .

(This is because 4 out of 12 marbles are red and 412 reduces to 1 by 3 .

The probability of selecting a red marble the second time is 1 by 3 .

The marble selections are independent and you can multiply the two probabilities to get the following:

probability of getting 2 reds = (1 by3)2

=1 by 9 .

1. So the probability of getting two reds is 1 by 9 .