3. Suppose you take 4 different routes to Trenton, the 3 different routes to Philadelphia. How many different routes can you take for the trip to Philadelphia by way of Trenton? ________ • _________ Trenton Philadelphia ___ 4 ____ • ___3_____ 12
Jan 04, 2016
3. Suppose you take 4 different routes to Trenton, the 3 different routes to Philadelphia.
How many different
routes can you take
for the trip to
Philadelphia by way
of Trenton?
________ • _________
Trenton Philadelphia
___4____ • ___3_____
12
4. You have 10 pairs of pants, 6 shirts, and 3 jackets.
How many outfits
can you have
consisting of a
shirt, a pair of
pants, and a
jacket?
______•______•______
Shirts Pants Jackets
___6__•__10__•__3___
180
5. Fifteen people line up for concert tickets. a) How many
different
arrangements are
possible?
15•14•13•12•11•10•9•8•
7•6•5•4•3•2•1 =
1,307,674,368,000
b) Suppose that a
certain person must
be first and another
person must be last.
How many
arrangements are now
possible?
1•13•12•11•10•9•8•
7•6•5•4•3•2•1•1 =
6,227,020,800
6) Using the letters A, B, C, D, E, Fa) How many “words”can be made using all 6letters?6 • 5 • 4 • 3 • 2 • 1 = 720b) How many of thesewords begin with E ?1 • 5 • 4 • 3 • 2 • 1 = 120c) How many of thesewords do NOT beginwith E? 720 –120 = 600d) How many 4-letterwords can be made ifno repetition is allowed?6•5•4•3 = 360
e) How many 3-letterwords can be made ifrepetition is allowed?6 • 6 • 6 = 216f) How many 2 OR 3letter words can bemade if repetition isnot allowed? 6•5+6•5•4 = 30 + 120 = 150g) If no repetition isallowed, how manywords containing atleast 5 letters can bemade? (both letter 6a)720 + 720 = 1440
16.3 Distinguishable Permutations
OBJ: To find the quotient of numbers given in factorial notation
To find the number of distinguishable permutations when some of the objects in an arrangement are alike
EX: Find the value of 8! _ 4! x 3!
One Method
8 • 7 • 6 • 5 • 4 • 3 • 2 • 1
4 • 3 • 2 • 1 • 3 • 2 • 1
Short Method
8 • 7 • 6 • 5 • 4!4! • 3 • 2 • 11680 6280
EX: Find the value of 6! _ 4! x 2!
Short Method
6 • 5 • 4!4! • 2 • 130 2
15
EX: Find the value of 12! _ 3! x 9!
Short Method
12 • 11 • 10 • 9!3 • 2 • 1 • 9!1320 6
220
NOTE: The letters in the word Pop are distinguishable since one of the two p’s is a capital letter. There are 3!, or 6, distinguishable permutations of P, o, p.
Pop Ppo oPp opP poP pPo
In the word pop, the two p’s are alike and can be permuted in 2! ways. The number of distinguishable permutations of p, o, p is 3! , or 3.
2!
pop ppo opp
The number of distinguishable permutations of the 5 letters in daddy is 5! 3! since the three d’sare alike and can be permuted in 3! ways.
DEF: Number of Distinguishable PermutationsGiven n objects in which a of them are
alike, the number of distinguishable
permutations of the n objects is n!
a!
EX: How many distinguishable permutations can be formed from the six letters in pepper? 6!__
3! • 2!
6 • 5 • 4 • 3!3! • 2 • 1
60
EX: How many distinguishable six- digit numbers can be formed from the digits of 747457? 6!__
3! • 2!
6 • 5 • 4 • 3!3! • 2 • 1
60
EX: How many distinguishable signals can be formed by displaying eleven flags if 3 of the flags are red, 5 are green, 2 are yellow, and 1 is white? 11!______
3! • 5! • 2! • 1!11 • 10 • 9 • 8 • 7 •6 •5!3 • 2 • 1 •5! • 2 •1 •1332640 1227720
16.4 Circular Permutations
OBJ: To find the number of possible permutations of objects in a circle
NOTE: Three objects may be arranged in a line in 3!, or 6, ways. Any one of the objects may be placed in the first positionABC ACB BAC BCA CAB CBA
In a circular permutation of objects, there is no first position. Only the positions of the objects relative to one another are considered.EX: In the figures below, Al, Betty and
Carl are seated in a circular position with
each person facing the center of the
circle.
In each of the first three figures, Al has Betty to his left and Carl to his right. This is one circular permutation of Al, Betty, and Carl.
A
C B
C
B A
B
A C
The remaining three figures each show Al with Betty to his right and Carl to his left. Again, these count as only one circular permutation of the three
A
B C
B
C A
C
A B
DEF: Number of Circular Permutations
The number of circular permutations of n distinct objects is (n-1)!
EX: A married couple invites 3 other couples to an anniversary dinner. In how many different ways can all of the 8 people be seated around a circular table?(8 – 1)!
7!
5040
7. How many distinguishable permutations can be made using
all the letters of:a) GREAT
5 • 4 • 3 • 2 • 1
5! = 120
b) FOOD
4! = 4 • 3 • 2!
2! 2!
12
c) TENNESSEE
9!
4! 2! 2!1!
9 • 8 • 7 • 6 • 5 • 4!
4! 2 • 2
15,120
4
= 3,780