Probability of Simple Events Lesson 8-1 Probability of Simple Events

Definitions Outcome- The number possible. Sample Space- A list of all possibilities Random- outcomes occur by chance.

Simple Event- a specific outcome or type of outcome Probability- the chance an event will happen. It compares the number of favorable outcomes to number of possible outcomes. Complementary Events- opposite events that add up to 1 in chances.

Formula Number of favorable outcomes P (event) = Number of possible outcomes

Example 1 A box contains 5 green pens, 3 blue pens, 8 black pens, and 4 red pens. A pen is picked at random. What is the probability the pen is green? There are 5 + 3 + 8 + 4 or 20 pens in the box. The probability the pen is green is ¼. The probability can also be written as 0.25 or 25%.

Example 2 A box contains 5 green pens, 3 blue pens, 8 black pens, and 4 red pens. A pen is picked at random. What is the probability the pen is blue or red? There are 5 + 3 + 8 + 4 or 20 pens in the box. The probability the pen is blue or red is 7/20. The probability can also be written as 0.35 or 35%.

Example 3 A box contains 5 green pens, 3 blue pens, 8 black pens, and 4 red pens. A pen is picked at random. What is the probability the pen is gold? There are 5 + 3 + 8 + 4 or 20 pens in the box. Since there are no gold pens, the probability is 0.

A bag contains 5 blue marbles, 10 red marbles, and 10 yellow marbles A bag contains 5 blue marbles, 10 red marbles, and 10 yellow marbles. A marble is picked at random. What is the probability the marble is yellow?

A bag contains 5 blue marbles, 10 red marbles, and 10 yellow marbles A bag contains 5 blue marbles, 10 red marbles, and 10 yellow marbles. A marble is picked at random. What is the probability the marble is blue or red?

A bag contains 5 blue marbles, 10 red marbles, and 10 yellow marbles A bag contains 5 blue marbles, 10 red marbles, and 10 yellow marbles. A marble is picked at random. What is the probability the marble is white?

Example 4 A computer company manufactures 2,500 computers each day. An average of 100 of these computers are returned with defects. What is the probability that the computer you purchased is not defective? 2500 – 100 or 2400 computers were not defective. The probability that your computer is not defective is 24/25 or 96%

One town has 10,000 phone numbers in use One town has 10,000 phone numbers in use. Of these, 500 are not listed in the local phone book. What is the probability that the number you are looking for is listed in the phone book? 10000 – 500 or 9500 numbers are listed. The probability that the number you are looking for is listed is 19/20 or 95%