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Math Help - Factors and Multiples

  1. #1
    Junior Member MoniMini's Avatar
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    Post Factors and Multiples

    I want to know how to do these 2 types of sums in an easier method......

    1. The smallest 4 digit number exactly divisible by 12, 15, 20 and 35.

    2. The least number when divided by 7, 10, 15 and 21 leaves 5, 8, 13 and 19 respectively as remainders.

    Thanks
    MoniMini @(^_^)@
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  2. #2
    MHF Contributor alexmahone's Avatar
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    1. lcm(12,15,20,35)=420
    The smallest 4 digit number exactly divisible by 12, 15, 20 and 35 is 420x3=1260.
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  3. #3
    Junior Member MoniMini's Avatar
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    Quote Originally Posted by alexmahone View Post
    1. lcm(12,15,20,35)=420
    The smallest 4 digit number exactly divisible by 12, 15, 20 and 35 is 420x3=1260.
    But why are we taking 3?
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  4. #4
    MHF Contributor alexmahone's Avatar
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    Quote Originally Posted by MoniMini View Post
    But why are we taking 3?
    420x2=840, which has only 3 digits. But 420x3=1260, which has 4 digits as required.
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  5. #5
    Junior Member MoniMini's Avatar
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    Quote Originally Posted by alexmahone View Post
    420x2=840, which has only 3 digits. But 420x3=1260, which has 4 digits as required.
    Okay!!! Thanks a LOTTTT!
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