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Permutation Q

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Permutation Q

by vineetbatra » Sat Jun 13, 2009 7:34 am
I am a complete daft in Permutation and will need help to understand this rudimentary q.

Janice is decorating her house with christmas lights. Christmas Lights are available in 7 colors, however she has money to buy only 6. What is the maximum number of light decoration she can create if she has to use all the light decorations she has purchased.

Now the OA says, 6! becuase she has to arrange 6 lights. Now my question is she also has the option of buying 6 out of 7 colors, so ideally it should be 6! * number of ways she can buy 6 lights from 7 colors.

Please explain with as much detail as possible.

Really appreciate.

Thanks

Vineet
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by tohellandback » Sat Jun 13, 2009 8:05 am
i think you are right. it has to be 6!*7
The powers of two are bloody impolite!!
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by rah_pandey » Sat Jun 13, 2009 10:29 pm
The question says "What is the maximum number of light decoration she can create if she has to use all the light decorations she has purchased."

This means we are concerned with the event after the purchase has happened. Thus the answer 6! looks correct. One more advice for Permutation and combination topics. DO NOT USE formulas. Try to develop the logic. Dont try to plug in values in formulaes directly. If you move step by step, your confidence will increase. Formulas are for advanced users.
Basically Combination is the heart and permutation is an extension. Permutation comes into picture once order of selection is important.
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by Naruto » Sun Jun 14, 2009 1:52 am
rah_pandey wrote:The question says "What is the maximum number of light decoration she can create if she has to use all the light decorations she has purchased."

This means we are concerned with the event after the purchase has happened. Thus the answer 6! looks correct. One more advice for Permutation and combination topics. DO NOT USE formulas. Try to develop the logic. Dont try to plug in values in formulaes directly. If you move step by step, your confidence will increase. Formulas are for advanced users.
Basically Combination is the heart and permutation is an extension. Permutation comes into picture once order of selection is important.
i agree with you.
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by vineetbatra » Sun Jun 14, 2009 2:28 pm
makes sense. Thanks rah_pandey.

Vineet
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