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Math Help - perfect square

  1. #1
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    perfect square

    What is the smallest positive integer which multiplied by 40 gives a perfect square?
    (A) 2 (B) 5 (C) 20 (D) 40 (E) None of these
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  2. #2
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    Quote Originally Posted by sri340 View Post
    What is the smallest positive integer which multiplied by 40 gives a perfect square?
    (A) 2 (B) 5 (C) 20 (D) 40 (E) None of these
    10, but in the given choices it is missing. So the choice is.......?
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  3. #3
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    Quote Originally Posted by sri340 View Post
    What is the smallest positive integer which multiplied by 40 gives a perfect square?
    (A) 2 (B) 5 (C) 20 (D) 40 (E) None of these

    40=2^3\cdot 5\Longrightarrow you have to make both 2 and 5 to have even powers, so...

    Tonio
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