Chapter 1.6 Probability Objective: Students set up probability equations appropriately

Experimental Probability  Probability of event =  Number of times event occurs Number of trials

Example 1  A player hit the bull’s eye on a circular dartboard 8 times out of 50. Find the experimental probability that the player hits the bull’s eye.

We need to use the formula.  Number of times event occurs = Number of trials

Example 2  Find the theoretical probability of rolling a multiple of 3 with a number cube? How about rolling an odd?  The Cube is a normal six sided di.

 A) How many numbers on the cube are a multiple of 3? Yes 2 numbers, 3 and 6.  So we get… 2 =  B) How many numbers are odd? Yes 3 numbers, 1,3,5 So we get… 3 = 1 6 2

Example 3  Suppose that all the points on the circular dartboard shown below are equally likely to be hit by a dart you have thrown. Find the probability of only scoring 2 points with one throw.  Note: The radius of each circle is one unit larger than the one below it Experimental Probability

 First we need to find the area of the whole dart board. This is the denominator because any throw can hit any where on the dart board.  To find the area of the green we need to subtract the areas of the others. So we get (using area πr 2 of a circle)  π(4r) 2 – π(3r) 2 π(4r) 2 = 16πr 2 - 9πr 2 16πr 2 = 7πr 2 16πr

 P. 42 (1- 19) odd  Omit 3 and 5