Find the number of permutations in the word CIRCUS.

Question

dumbcow · Answer

there are 6 letters ... total ways to arrange them is 6!

there are 2 letters that are the same, "C" , total ways to arrange them is 2!

---->  6!/2!

anonymous · Answer

360?

anonymous · Answer

@dumbcow  ind the number of ways to listen to 4 CDs from a selection of 8 CDs. I got 70 for this, is this right?

dumbcow · Answer

haha sorry you are right its 360

dumbcow · Answer

selecting 4 cds in order from 8 is 8P4

--> 8!/(8-4)! = 8*7*6*5 = 1680

dumbcow · Answer

or if its not in order .... 8 choose 4 = 70 as you said

anonymous · Answer

So how can I tell the difference whether Im suppose to do 8P4 or (8!)/(8-4)!?

dumbcow · Answer

8P4 = 8!/(8-4)!

anonymous · Answer

but doesnt 8!/(8-4)! = 70?

anonymous · Answer

Find the number of ways to listen to 4 CDs from a selection of 8 CDs.
	A.	1,680
	B.	336
	C.	70
	D.	50
 I get both option XD

dumbcow · Answer

no
$$\frac{8!}{4! 4!} = 70$$
this is combinations 
$$\frac{8!}{4!} = 1680$$
this is permutations

dumbcow · Answer

i hate when its ambiguous, in this case though i would assume combinations because it does not exactly imply order or arrangement

anonymous · Answer

OH! that makes sense, How many different 12-member juries can be chosen from a pool of 35 people? This would be 834,451,800  right ? I did 35!/(35-12)!

anonymous · Answer

Yeah, I'm not a big fan of how they ask questions, it's either not clear or specified

dumbcow · Answer

for this one they give a hint, they use the word "chosen" so should you use combinations or permutations ?

anonymous · Answer

combo?

dumbcow · Answer

yep , it doesn't matter what order the jury is selected

you gave the answer for permutatuons

anonymous · Answer

How many different 12-member juries can be chosen from a pool of 35 people?
	A.	534,451,800
	B.	634,451,800
	C.	734,451,800
	D.	834,451,800
The are the answers the gave me to choose from x)

dumbcow · Answer

$$\rightarrow \frac{35!}{12! 23!}$$

anonymous · Answer

How do I solve that? lol

dumbcow · Answer

oh haha your answer is correct but you wrote the wrong formula

dumbcow · Answer

with a calculator :)

anonymous · Answer

Oh ok, I wrote it wrong then, I dont use a calculator XD another question 

Find the number of permutations of the first 10 letters of the alphabet taking 2 letters at a time. 

For this one would it be 10!/2!?

dumbcow · Answer

http://www.mathwords.com/c/combination_formula.htm http://www.mathwords.com/p/permutation_formula.htm

dumbcow · Answer

ok you are taking 2 letters out of total selection of 10 letters.
it says use permutations

--> 10!/(10-2)! = 10!/8! = 10*9 = 90

anonymous · Answer

OH alright! In how many ways can a teacher arrange 5 students in the front row of a classroom with a total of 20 students? So this one its asking combo but when i do the combo I dont come up with any of the option. A.	860,480
	B.	2,860,480
	C.	60,480
	D.	1,860,480
 but if i do permutation i get D

dumbcow · Answer

it says "arrange", arranging implies a specific order ... use permutations

anonymous · Answer

and different ways would be combo! Ok thank you so much

dumbcow · Answer

yw