Transcript Sec1.6 Probability ppt

Chapter 1.6
Probability
Objective: Students set up
probability equations
appropriately
Experimental
Probability
Probability
Number
of event =
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
8
 16%
50
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 = 1
6
3
 B) How many numbers are odd?

Yes 3 numbers, 1,3,5
So we get…
3 = 1
6
2
Experimental Probability
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.
20
20

10
5
2


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 πr2 of a circle)
π(4r)2 – π(3r)2
π(4r)2
= 16πr2 - 9πr2
16πr2
7
= 7πr2

16πr2
16

20
20
10
5
2
P.
42 (1- 19) odd
Omit 3 and 5