Transcript Counting Rule

WARM UP
1)
JoJo and Kiki are visiting the Empire State Building.
Each of them enters a different elevator in the main
lobby that can let them off on any floor from 1 to 3.
Assuming that they are as likely to get off at one floor
as another, what is the probability that they both get
off on the same floor?
2)
A family plans to have 2 children. What is the
probability that both children will be girls?
3)
What is the probability of getting a black jack?
HOMEWORK
4) a) 126/316
b) 5/316
c) 8/316
8) 4 drunks, 4 Jackets
10) 3 patients, 3 samples
12) 10,000 microwaves, recalled ones with last digit
of 5, 6, or 7
Section 4.3
Counting Rule
An easy way to find total
possibilities or the
SAMPLE SPACE
Counting Rule
MULTIPLY
LICENSE PLATES

In Delaware, license plates have seven
characters. How many possibilities are there
total?
36·36·36·36·36·36·36=
26·25·24·23·22·21·20=
 What if you could only use numbers?
7.836
10
 What if you could only
use E
letters?
3,315,312,000
10·10·10·10·10·10·10=
 What if you can’t repeat letters?
26·26·26·26·26·26·26=
 What if you do not have
any restrictions at
10,000,000
8,031,810,176
all?
PASSWORDS


Most internet sites force you to have a
password.
If one site requires 8 characters,
letters only, how many possibilities are
there?
26·26·26·26·26·26·26·26=
2.088 E 11
CELL PHONES


How many phone numbers are possible in
Delaware?
Are there enough possibilities if everyone
had their own cell phone? (There are about
850,000 people living in Delaware)
(302)…-….
1·1·1·8·10·10·10·10·10·10=
8,000,000
DIGITS
How many five digit numbers can be formed
from the digits 2, 4, 5, 6, 7 if the number
must be bigger than 50,000 without
repetition?
__
If we
allowed
· __
· __ repetition,
· __ · __ how many
possibilities are there?

3·4·3·2·1=
3·5·5·5·5=
72
1,875
waysways
__ · __ · __ · __ · __