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Thread: square roots

  1. September 19th 2008, 08:42 AM #1
    fabxx
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    square roots

    Page 473 #7
    If 18\sqrt{18}= r\sqrt{t}, where r and t are positive integers and r>t, which of the following could be the value of rt? I don't get why the answer is 108. Thanks in advance.
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  2. September 19th 2008, 08:54 AM #2
    Moo
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    Hello,
    Quote Originally Posted by fabxx View Post
    Page 473 #7
    If 18\sqrt{18}= r\sqrt{t}, where r and t are positive integers and r>t, which of the following could be the value of rt? I don't get why the answer is 108. Thanks in advance.
    18=9 \times 2=2 \cdot 3^2

    Hence \sqrt{18}=\sqrt{3^2 \cdot 2}=3 \sqrt{2}

    So 18 \sqrt{18}=\dots

    Can you finish it ?
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  3. September 19th 2008, 09:11 AM #3
    fabxx
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    I multiplied and I got 54 sqrt(2) which isn't correct since the correct answer from the book is 108. Why though?
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  4. September 19th 2008, 09:15 AM #4
    Moo
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    Quote Originally Posted by fabxx View Post
    I multiplied and I got 54 sqrt(2) which isn't correct since the correct answer from the book is 108. Why though?
    54 \sqrt{2}=r \sqrt{t}
    So r=54 and t=2

    You're asked for rt, that is to say 54x2
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