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d77
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 Posted: Wed Dec 13, 2006 6:20 am Post subject: from gmatprep |
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If k is a positive integer and the tens digit of k+5 is 4, what is the tens digit of k
1. k>35
2.the unit sigit of k is greater then 5
why is
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zipper123
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| Posted: Wed Dec 13, 2006 7:14 am Post subject: Re: from gmatprep |
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| d77 wrote: | If k is a positive integer and the tens digit of k+5 is 4, what is the tens digit of k
1. k>35
2.the unit sigit of k is greater then 5
why is
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1) is not sufficient, because the k can be 37 or 42, which does not provide a unique answer.
Whereas:
2) consider the followings:
If the unit digit is less then 5,
--> k's tens digit is 4
if the unit digit is more than 5,
--> k's tens digit is 3
Therefore condition 2) is sufficient, because it restricts the tens digit to be 3 only.
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d77
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| Posted: Thu Dec 14, 2006 11:15 am Post subject: thanks |
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