Super confusing permutation and combination question for me

[zeebujha]

Okay, I made this question on my own and as expected I couldn't solve this question.
So, here is the question:
In how many ways can 3 of the letters chosen from the given set be arranged:
AAABBBCCCDDDEEF

That is first you have to choose 3 letters and then arrange them. In how many ways can this be done??

This question comes from my inability to solve the general type of question: What if there are n letter, s to be chosen, one letter repeated r times, another q times, another p times .......................

 

[ahmed t]

Re: Super confusing permutation and combination question for

you dont need to know how to select things where there are identical objects
not in our syllabus

 

[borntofly]

Re: Super confusing permutation and combination question for

6C3 X 3!

You have to assume the repeated objects as one unit.

 

[ahmed t]

Re: Super confusing permutation and combination question for

thats wrong
then you are assuming you can only pick one of each letter
eg ABC
but you could pick
AAB, couldn't you
this is not in our syllabus and im sure of that

 

[borntofly]

Re: Super confusing permutation and combination question for

4C3 X 3!

 

[borntofly]

Re: Super confusing permutation and combination question for

thats wrong
then you are assuming you can only pick one of each letter
eg ABC
but you could pick
AAB, couldn't you
this is not in our syllabus and im sure of that

yeah we don't have to that .. i was trying to solve it

 

[BILALrox01]

Re: Super confusing permutation and combination question for

Since you said arrangement.. 15!/(3!*3!*3!*3!*3!)

 

[ahmed t]

Re: Super confusing permutation and combination question for

read the question properly bilal

 

[BILALrox01]

Re: Super confusing permutation and combination question for

Whats the use of solving the question u can't understan.. I don't think the one who wrote it understands it himself/herself.
But could you enlighten me about what i didn't read properly??

 

[zeebujha]

Re: Super confusing permutation and combination question for

Whats the use of solving the question u can't understan.. I don't think the one who wrote it understands it himself/herself.
But could you enlighten me about what i didn't read properly??

The question requires you to choose 3 of the given objects and arrange them. This basically is a problem stating in how many ways can you arrange any 3 of the given objects. (This question is tricky because we have restricted the number as well as included case of permutation. I think our syllabus either restricts the number or gives the repetition problem but doesn't combine them together). I could solve this if the types of letter were small, say 2 or 3 but I have created problems for myself by choosing 6 letters,lol. Surely, we won't be asked this!

 

[awesome94]

Re: Super confusing permutation and combination question for

when do u use permutations and combinations,
anyone got some hints to make this topic little less torturous.
PLEASE!!!

 

[zeebujha]

Re: Super confusing permutation and combination question for

permutation is when we are ARRANGING objects
combination is when we are SELECTING objects
So, permutation we have to first SELECT and then ARRANGE
For, combination, we only have to SELECT and not worry about arranging.

 

[awesome94]

Re: Super confusing permutation and combination question for

okay... thanks!
how would you do this::
http://www.xtremepapers.me/CIE/Internat ... _qp_61.pdf
q6(ii)

 

[zeebujha]

Re: Super confusing permutation and combination question for

okay... thanks!
how would you do this::
http://www.xtremepapers.me/CIE/Internat ... _qp_61.pdf
q6(ii)

First picture the 6 plastic mugs kept on a table with gaps between each of the cups. Now, if the china mugs are to kept separate from each other, then they have to be placed between the spaces of the plastic mugs and never together. When six plastic mugs are kept side by side, there are seven spaces available. So, now this boils down to a simple case of placing three different objects in 7 spaces or put simply choosing 3 spaces out of the seven available spaces (placing the china mugs in a gap is akin to choosing the gap). So, we can choose the 3 spaces in 7P3 i.e. 210 ways. But, the 6 plastics mug,each being distinct, can be arranged in 6! different ways as well. So,you would have to multiply the two : 210x6! (as the two are independent events and occur at the same time). So, the answer is : 210x6!=151200

Hope this helped!

 

[sksuriza]

Re: Super confusing permutation and combination question for

wt abt
15C3 x 3!

 

[awesome94]

Re: Super confusing permutation and combination question for

Great! thanks!