Question #2ce41

1 Answer
Oct 24, 2017

2/25, 9/100, 3/50 respectively

Explanation:

The bag contains in total 4 + 6 + 8 + 2 = 20 marbles.

The probabilities for each colour are as follows:

Blue: 4/20 = 1/5

Red: 6/20 = 3/10

Green: 8/20 = 2/5

Yellow: 2/20 = 1/10

For a probability of one thing followed by another, you simply multiply the two probabilities, so

P("B then G") = 1/5 xx 2/5 = 2/25

P("R then R") = 3/10 xx 3/10= 9/100

P("Y then not G") = ?

This last one is slightly trickier. The probability of something not happening is 1 minus the probability that it will happen, or

P(barX) = 1-P(X)

therefore

P(barG) = 1-2/5 = 3/5

so

P("Y then not G") = 1/10 xx 3/5 = 3/50