Question

There is a bag filled with 4 blue and 5 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 at least 1 red?

Answer 1

"at least 1 red" also means "not 2 blue"

p(not blue) = 5 / (4 + 5) = 5/9

p(at least 1 red) = 1 - (5/9)^2