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Math Help - SAT question

  1. #1
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    SAT question

    All numbers divisible by both 4 and 15 are also divisible by which of the following?

    A. 6
    B. 8
    C. 18
    D. 24
    E. 25

    explain please thanks
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  2. #2
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    e^(i*pi)'s Avatar
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    Re: SAT question

    The LCM of 4 and 15 is 60.

    So which of those numbers is a factor of 60?
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  3. #3
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    Re: SAT question

    6 thanks, so if a number is factor of a LCM of two number, they can divide evenly multiples of those two number
    Quote Originally Posted by e^(i*pi) View Post
    The LCM of 4 and 15 is 60.

    So which of those numbers is a factor of 60?
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  4. #4
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    Re: SAT question

    Quote Originally Posted by RK29 View Post
    6 thanks, so if a number is factor of a LCM of two number, they can divide evenly multiples of those two number
    Yes, that's it exactly. It also holds for the LCM of more than two numbers.

    For example the LCM of 2,3 and 8 is 24 so any other factor of 24 will divide by multiples of 2,3 and 8
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  5. #5
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    Re: SAT question

    what's a quick way to find LCM and GCF? i am having hard time.
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  6. #6
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    Re: SAT question

    Quote Originally Posted by RK29 View Post
    what's a quick way to find LCM and GCF? i am having hard time.
    LCM and GCF

    Prime factors are the easiest way, the link above explains it better than I can
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  7. #7
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    Re: SAT question

    I learned that way when i was young, they complicated stuff over years
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