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Re: Permutation Help required!! [#permalink]
Biggest question here is whether digits can be re-used or not.
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Re: Permutation Help required!! [#permalink]
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why not to count how many ALL (even&odd) numbers of 3 digit and than half of that would be even?

so (7!/4!)/2 is 105
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Re: Permutation Help required!! [#permalink]
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Andrusha wrote:
guys
why not to count how many ALL (even&odd) numbers of 3 digit and than half of that would be even?

so (7!/4!)/2 is 105


Given digits 0-6, in how many ways can you make 3 digit numbers?

If you re-use the digits: 6*7*7 (which is the case in the question since it doesn't say that you cannot re-use)
If you do not re-use the digits: 6*6*5

How did you get 7*6*5?

Also number of even and odd numbers would be equal if you have equal even and odd digits. Here you have 4 even digits (0, 2, 4, 6) and 3 odd digits (1, 3, 5). Also 0 complicates the matter because the number cannot have 0 at hundred's place. So number of numbers ending in 0 is not the same as number of numbers ending in 1 or 2 or 3....
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Re: Permutation Help required!! [#permalink]
Thanks guys for the reply..
T
I came across this question in urch website. The question doesn't mention whether the digits can be re-used or not. I guess in the gmat exam, the problem wud clearly state with or without repetition.

Anuu
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Re: Permutation Help required!! [#permalink]
I also think the order in which we choose the digit matters. Primarily we MUST choose the unit's digit first - its the most restricted digit. And then we must choose a non-zero hundred's digit and finally the ten's digit.



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