Question

A box contains 19 large marbles and 11 small marbles. Each marble is either green or white. 5 of the large marbles are green, and 3 of the small marbles are white. If a marble is randomly selected from the box, what is the probability that it is small or green? Express your answer as a fraction or a decimal number rounded to four decimal places.

Answer 1

L: large marbles

S: Small marbles

G: Green marbles

and W: White marbles

So, there are (19+11) = 30 marbles in total.

We have to find P[S U G].

by Total probability theorem.

Now, P[S] = 11/30

  

and  

So,