E N D
WARM UP • 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? • A family plans to have 2 children. What is the probability that both children will be girls? • 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 4.3Counting Rule An easy way to find total possibilities or theSAMPLE SPACE
Counting Rule MULTIPLY
LICENSE PLATES • In Delaware, license plates have seven characters. How many possibilities are there total? • What if you could only use numbers? • What if you could only use letters? • What if you can’t repeat letters? • What if you do not have any restrictions at all? 36·36·36·36·36·36·36= 7.836 E 10 26·25·24·23·22·21·20= 3,315,312,000 10·10·10·10·10·10·10= 10,000,000 26·26·26·26·26·26·26= 8,031,810,176
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= 72 ways 3·5·5·5·5= 1,875 ways __ · __ · __ · __ · __