Results 1 to 3 of 3

Math Help - Divisibility Tests

  1. #1
    Member
    Joined
    Mar 2007
    From
    England
    Posts
    104

    Divisibility Tests

    I would like some help in finding the divisibility tests for when integers are divisible by 4 and 8.

    The hint given in the book is to write the integer as:
    N=100M+10P+R=10P+R (Mod 4). I'm unclear about where this comes from or how it helps me in answering the question. Help would be greatly appreciated.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by free_to_fly View Post
    I would like some help in finding the divisibility tests for when integers are divisible by 4 and 8.

    The hint given in the book is to write the integer as:
    N=100M+10P+R=10P+R (Mod 4). I'm unclear about where this comes from or how it helps me in answering the question. Help would be greatly appreciated.
    This tells you that an integer is divisible by 4 if the number made from the two least significant digits is divisible by 4.

    This is true because if N is the number M the number made from the two least significant digits, then:

    N=100k + M

    for some integer k. But 100 is divisible by 4, hence N is divisible by 4 if and only if M is divisible by 4.

    RonL
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Hello,

    Same goes for divisibility by 8.

    N=1000k+M.

    1000 is divisible by 8, so N is divisible by 8 iff M is divisible by 8.

    We can go further & use the hint given.
    N=100M+10P+R (mod 8)
    If M is even, then 100M is divisible by 8 (check it out), and then we'll care only about the 2 last digits.
    If M is odd, then...
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Power tests
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: April 11th 2010, 07:14 PM
  2. Tests
    Posted in the Algebra Forum
    Replies: 6
    Last Post: November 13th 2008, 05:43 AM
  3. Chi-tests
    Posted in the Statistics Forum
    Replies: 0
    Last Post: April 19th 2008, 12:24 PM
  4. series tests
    Posted in the Calculus Forum
    Replies: 2
    Last Post: July 5th 2007, 07:02 PM
  5. Placement tests
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: June 18th 2007, 01:04 PM

Search Tags


/mathhelpforum @mathhelpforum