Question

There is a bag filled with 5 blue and 4 red 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 of the same colour?

Answer 1

5 blue, 4 red = 9 total

Probability (Blue, Blue) = 5/9 x 5/9 = 25/81 = 0.30864

Probability (Red, Red) = 4/9 x 4/9 = 16/81 = 0.19753

Probability (Blue,Blue) or (Red,Red) = 25/81 + 16/81 = 41/81 = 0.506173

Fraction answer = 41/81

Decimal answer = 0.506173 (round off as needed)