Probability homework

Question

A bag consists of 4 different colored marbles. The probability of drawing each is as follows:

P(Blue)= .4

P(Red)= .2

P(Purple)= .3

P(Black)= .1

You draw a marble out of the bag and then replace it. What is the probability that you draw:

1. A red marble first then a blue marble second?
2. A black marble first and purple second?
3. A red of blue marble
4. A gray marble?

Answer 1

1) P(rb) = .2x.4 = .08

2) P(black then purple) = .1x.3 = .03

3) P(at least one red or blue with 2 draws with replacement) = 1- .4^2 = .86

4) P(grey)= 0