Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Factoring: What am I doing wrong?

  1. Feb 4, 2007 #1
    In adding fractions with denominators of 33 and 48, the LCD is 240.

    I don't understand any easy way to arrive at this number.

    33 factors out to be : 3 * 11
    48 factors out to be: 2 * 2 * 2 * 2 * 3

    But from these numbers, none will yeild a product of 240.

    What am I doing wrong?
     
  2. jcsd
  3. Feb 4, 2007 #2
    What is the LCD? Did you meand the GCD(Greatest Common Divisor)? Or did you mean the LCM(Least Common Multiple)? As far as I can tell you did nothing wrong, as 240 is neither the gcd nor the lcm of 33 and 48.

    EDIT: Oh I guess you meant LCD as in Least Common Denominator, which would be equivalent in this case to the LCM, but still it shouldn't be 240, and you should be able to tell that from the prime factorizations of the three numbers.
     
    Last edited: Feb 4, 2007
  4. Feb 4, 2007 #3
    My mistake!

    The denominators of the fractions were 30 (not 33) and 48, and the LCD is in fact 240. I read the problem wrong!

    30 = 2 * 3 * 5
    48 = 2 * 2 * 2 * 2 * 3

    2 * 2 * 2 * 2 * 3 * 5 = 240

    Thanks for help. I appreciate it.
     
    Last edited: Feb 4, 2007
  5. Feb 5, 2007 #4

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    LCD is is trivially 1 for all natural numbers.

    What you are after is LCM, least common multiple.
     
  6. Feb 5, 2007 #5

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Yes, arildno, he is looking for the least common multiple of the numbers he gave. He did, however, say initially that these were the denominators of given fractions and he was looking for the least common denominator of those fractions.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Factoring: What am I doing wrong?
  1. What am I doing wrong? (Replies: 2)

  2. What am i doing wrong (Replies: 2)

  3. What am I doing wrong? (Replies: 6)

Loading...