GMAT Forum
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- yamini
General Combination question
5 pens - 2 white, 2 black, 1 read. How many ways these pens can be arranged?
- shaji
Re: General Combination question
yamini Wrote:5 pens - 2 white, 2 black, 1 read. How many ways these pens can be arranged?
The problem does not clarfify whether the like colored pens are similar in all other respects, if so then the # of arrangements are 30ways otherwise its 120.
- RonPurewal
- Students
- Posts: 19744
- Joined: Tue Aug 14, 2007 8:23 am
Please post a source for every question. If you made up the question (certainly a reasonable possibility here), then say so!
If the white pens are indistinguishable and the black pens are indistinguishable, then the total # of combinations is 5! / (2! 2! 1!), which is 30. Check out the section about arranging letters in the strategy guide for more examples along these lines.
As a solidifying example, the number of different arrangements of the letters in MISSISSIPPI is 11! / (1! 4! 4! 2!). If you can explain to yourself why, then you're on your way.
If the white pens are indistinguishable and the black pens are indistinguishable, then the total # of combinations is 5! / (2! 2! 1!), which is 30. Check out the section about arranging letters in the strategy guide for more examples along these lines.
As a solidifying example, the number of different arrangements of the letters in MISSISSIPPI is 11! / (1! 4! 4! 2!). If you can explain to yourself why, then you're on your way.
3 posts Page 1 of 1