Results 1 to 3 of 3

Math Help - Bases

  1. #1
    Newbie
    Joined
    Apr 2005
    Posts
    2

    Bases

    Hi all.

    I simply want to know what is the best way to do sums in different bases. Base 10 is easy and we can all do sums with it but what if I had 342 - 173. In base 10 the answer is 169. Fine. But how would I go about solving it in base 9 or 8? What difference, in my mind, do I need to apply to make it easier to do?

    I have worked out that 169 in Base 9 is 207 and in Base 8 is 251 but I had to find the answer in Base 10 and then convert it and that just takes ages. There must be a simplier way.

    Also, If anyway can find the thread about working out square roots without a calculator I would be grateful.
    Last edited by Bobber; April 9th 2005 at 04:07 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Apr 2005
    Posts
    103
    342[8] - 173[8] = 147[8]

    Do it like:
    342
    - 173
    -------

    Instead of "borrowing" 10, borrow 8. Instead of bumping a digit at 10, bump at 8.


    ===================

    Newtons Approximation for Square Root
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,412
    Thanks
    1328
    paultwant is, of course, completely correct- you add and subtract in other bases exactly like you do in base 10 except that you "carry" or "borrow" the base rather than 10.

    A little more detail:
    342- 173 (base 9)
    Since "2" is smaller than "3" we "borrow 9: 9+ 2= 11 and 11- 3= 8 so we write "8" in the first place.
    Since we "borrowed", we now have "3" rather than "4" in the second place (9 is 10 in base 9). 7 is larger than 3 we borrow again: 9+3= 12 and 12- 7= 5 so we write "5" in the second place.
    Since we "borrowed", we now have "2" rather than "1" in the third place. 2- 1= 1 so we write "1" in the third place.
    In base 9, 342- 173 is 158.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Sub bases
    Posted in the Differential Geometry Forum
    Replies: 1
    Last Post: November 2nd 2010, 05:38 PM
  2. Bases
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: July 20th 2010, 10:45 PM
  3. bases
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: November 22nd 2009, 07:30 AM
  4. Bases
    Posted in the Algebra Forum
    Replies: 2
    Last Post: August 17th 2008, 02:53 PM
  5. Bases other than e... help?
    Posted in the Calculus Forum
    Replies: 12
    Last Post: August 31st 2007, 06:48 AM

Search Tags


/mathhelpforum @mathhelpforum