Calculate the introduction to Probability?

Probability refers to the chance that an event will happen. Probability is presented as the ratio of the number of ways an event can occur relative to the number of possible outcomes.
P(event) = (Number of ways an event can occur)/ (Number of possible outcomes)

Example 1:

If you pick from a bag that contains 2 blue marbles, 3 green marbles, and 4 red marbles, what's the probability of picking a red marble?

P(red) = Number of red marbles/ Total number of marbles
= 4/(2+3+4)
= 4/9 (about 44% chance)

Example 2:
If you roll a die, what's the probability of rolling:
a. a six?
b. an odd number?
c. a number less than 3?
Solution
a) P(Six) = 1/6 (about 17% chance)
b) P(odd: 1,3,5) = 3/6= ½ (50% chance)
c) P(<3:2,1) = 2/6 = 1/3 (33% chance)