Showing posts with label Counting Principle. Show all posts
Showing posts with label Counting Principle. Show all posts

Friday, January 2, 2015

Thursday, May 16, 2013

the number of ways of arranging 5 women and 4 men so that the row begin and end with women


Question 749359 in Permutations:
the number of ways of arranging 5 women and 4 men so that the row begin and end with women

5-ways to choose 1st person
4-ways to choose the last
(7)(6)(5)(4)(3)(2)(1) ways to choose middle people

total: 20(7!)=10800

:)

Tuesday, May 14, 2013

Seven flute players are listed in the program in random order. How many different ways can the names be listed?

Assuming they all have different names 7! 
(counting principle) 


Take a look: 
7 ways to list first name
6 ways for the second
5 for the third
4 the fourth
3 fifth
2 sixth
1 last 
the total number of ways is the product: 
(7)(6)(5)(4)(3)(2)(1)=7! 

:)

Monday, May 13, 2013

There are seven finalists for two scholarships. Four of them are girls and three of them are boys. In how many ways can the scholarships be awarded to one boy and one girl?

This is a counting problem perfect for the counting principle. 
4 ways to choose a girl
3 ways to choose a boy 
ways to choose a girl and a boy: (4)(3)=12

In how many ways can three student-council members be elected from five candidates?

This is a counting problem so we apply the counting principle 
5 - choices for 1st electee
4 - remaining choices for second electee
3 - are left 
# of choices : (5)(4)(3)= 60 
60 ways 


:)

Saturday, May 11, 2013

In how many ways can the word "TOPO" be arranged

The rule for repeated objects is 




(n!)/(m!*p!*...*q) 

so we get 
4%21%2F2%21=12 

:)

You have invited your friend over for dinner. You have . How many meal choices can you offer?

Let's use the counting principle to make our computation. 

three kinds of fish, 
four types of vegetables,
two kids of rice, and 
3 pints (types?) of ice cream 


leads us to 


# of meal choices: (3)(4)(2)(3)=72 

:)