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Lesson 70
Probability
Designated Order
Probability
• Probability = (number of desired outcomes)
(number of possible outcomes)
• Independent events: happens regardless of
anything else
Example 70.1
• A fair coin is tossed three times and comes up
heads every time. What is the probability on
the next toss that it will come up heads?
Example 70.2
• Six green marbles and eight red marbles are placed in
a bag. One marble is drawn and then dropped back in
the bag. Then, a second marble is drawn and
dropped back in the bag. Both marbles were red. If
another marble is drawn, what is the probability that it
will be red?
Example 70.3
• A single die is rolled three times. The
results are a 1, a 4, and a 3, in that order.
What is the probability that the next roll will
produce a number greater than 2?
Example 70.4
• Two dice are rolled. What is the probability
that the sum of the numbers rolled is (a) 7? (b)
a number greater than 8?
Dependent Events
• Events that must happen in a certain
order.
• Multiply the probabilities
Example 70.5
• A fair coin is tossed four times. What is the
probability that the first two times it comes up
heads, and the last two times it comes up tails?
Example 70.6
• The spinner shown is spun twice. What is
the probability that the spinner stops on 4
and then on 3?
4
1
3
2
Homework
• Practice a – e
• P.S. 70
• 1-5 all, 6-30 even