Question

There is a bag filled with 5 blue, 2 red and 3 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 2 different colours?

Answer 1

0.62

Explanation:

There are a total of 10 marbles in the bag.

P(blue and not blue) = 5/10 × 5/10 = 25/100

P(red and not red) = 2/10 × 8/10 = 16/100

P(green and not green) = 3/10 × 7/10 = 21/100

P = 25/100 + 16/100 + 21/100

P = 62/100

P = 0.62

Alternatively, you can calculate it this way:

P(both blue) = (5/10)² = 25/100

P(both red) = (2/10)² = 4/100

P(both green) = (3/10)² = 9/100

P = 1 − (25/100 + 4/10 + 9/100)

P = 1 − 38/100

P = 62/100

P = 0.62