Probability with balls, spheres or colored marbles. explanation of one of the classic examples to begin to understand the concept of probability, in this case of an exercise of probability of an event or simple experiment in which the law of Laplace is used, in the exercise: "In an urn there are 4 red, 2 blue and one yellow balls What is the probability of:
1. Take out a red ball.
2. Take out a blue or yellow ball.
Within the probability course.