Probability

Question

A bag contains 5 blue, 3 red, and 8 green marbles. You choose a marble, do not replace it, and then choose another. What is the probability that both marbles are red

Answer 1

There are 16 marbles.

 

The probability the first marble is red is 3/16.

 

After the first marble is drawn, there are 15 marbles left.

The probability of drawing another red marble is now 2/15

 

The probability both marbles are rd is (3/16)*(2/15) = 1/40 

Answer 2

P(both red) = ₃C₂ / ₁₆C₂

based on three red marbles, choose 2 compared to 16 total marbles, choose 2.