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Math Help - factors

  1. #1
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    factors

    {1,2,3,K 175,176,177,178 }

    How many numbers in the set above have 5 as a factor but do not have 10 as a factor?


    (A) 1 (B) 3 (C) 4 (D) 17 (E) 18
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  2. #2
    Senior Member Stroodle's Avatar
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    For a number to be divisible by 5, it's last digit must be either 5 or 0. For a number to be divisible by 10 its last digit must be 0.
    Hence for a number to have 5 as a factor, but not 10, it's last digit must be 5 only.

    One number in the set you posted has 5 as its last digit.
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  3. #3
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    Wouldn't that make the answer 17? Assuming the K is for all the numbers between 3 and 175...
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  4. #4
    Senior Member Stroodle's Avatar
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    Oh yeah. It's 17 if K is all real numbers between 3 and 175
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