Results 1 to 14 of 14

Math Help - Algebra: Multiplication!

  1. #1
    Member Sazza's Avatar
    Joined
    Apr 2007
    From
    Australia
    Posts
    98

    Smile Algebra: Multiplication!

    I just need some help clearing something up, that i don't quite understand:

    2/3 x 18c=2/3 x 18 x c
    = 12c
    ---------------
    That's Right, right? But how did i get the 2/3 x 18??? How was i mean't to get 12?
    This is out of a example page, when were talking about how any two terms can be multiplyed together!
    Can you help me clear this up?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Oct 2006
    Posts
    679
    Awards
    1

    Re:

    Wait is

    "x" a variable or are you trying to multiply? Please specify...
    Follow Math Help Forum on Facebook and Google+

  3. #3
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by qbkr21 View Post
    Wait is

    "x" a variable or are you trying to multiply? Please specify...
    no, apparently "x" is the multiplication sign, c is the variable
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member Sazza's Avatar
    Joined
    Apr 2007
    From
    Australia
    Posts
    98
    yeah, um.. What i'm trying to find out is, it says that 2/3 x 18 equals 12... as i wrote:

    it shows: 2/3 x 18c= 2/3 x 18 x c
    = 12c
    Follow Math Help Forum on Facebook and Google+

  5. #5
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by Sazza View Post
    yeah, um.. What i'm trying to find out is, it says that 2/3 x 18 equals 12... as i wrote:

    it shows: 2/3 x 18c= 2/3 x 18 x c
    = 12c
    we think of this as multiplying two fractions. when multiplying two fractions, we multiply the tops to get the top of the new fraction and multiply the bottoms to get the bottom of the new fraction. but we have the option of reducing things before doing that. if a number in the top has a common factor with a number in the bottom, we can divide that number out before multipying across.

    in this problem, we have 3 in the bottom of one fraction and 18 in the top of the other. we can divide 3 into 3 and get one, and we can divide 3 into 18 and get 6. so we divide the 3 out and leave these values. then we multiply across to get the new value
    Attached Thumbnails Attached Thumbnails Algebra: Multiplication!-numbers.jpg  
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Member Sazza's Avatar
    Joined
    Apr 2007
    From
    Australia
    Posts
    98

    Smile

    okay so i can
    • divide 3 into 3 and get 1 (3 divided by 3 = 1)
    • and i can divide 3 into 18, and get 6 i tryed that with my calculator and i get 0.1666666 ????
    • we divide (do you mean leave out?) the 3 out and leave these values.
    • Then we multiply across to get the new value......
    hang on i'm working this out... Do you think you can explain it differently?
    Follow Math Help Forum on Facebook and Google+

  7. #7
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by Sazza View Post
    okay so i can
    • divide 3 into 3 and get 1 (3 divided by 3 = 1)
    • and i can divide 3 into 18, and get 6 i tryed that with my calculator and i get 0.1666666 ????
    • we divide (do you mean leave out?) the 3 out and leave these values.
    • Then we multiply across to get the new value......
    hang on i'm working this out... Do you think you can explain it differently?
    what you did was divide 3 by 18, it should be the other way around

    look at the pic i posted. we divided 3 into 3 and the result was 1, so i replaced 3 with 1. on the top, i divided 3 into 18 as well and te result was 6, so i replace the 18 with 6. then i multiplied straight across on the top to get 12c and i multiplied straight across on the bottom to get 1 (6c = 6c/1) so the result is 12c
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Member Sazza's Avatar
    Joined
    Apr 2007
    From
    Australia
    Posts
    98

    Smile

    Oh okay! Thanks for explaining it again. Now i understand...

    2/1 x 18 = 2/1 x 6c = 12c

    Bottom: divide: 3 into 3 = 1 (replace 3 with 1)
    Top: 3 divided by 18 = 6, so replace the 18 with 6!
    I get it now...

    Also how would i work out a question like this: A Pool is twice as long as it is wide. It is w metres wide. How many metres long is the pool?
    I know you will have to find out how long the w is, but how would i do that?
    Follow Math Help Forum on Facebook and Google+

  9. #9
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by Sazza View Post

    Also how would i work out a question like this: A Pool is twice as long as it is wide. It is w metres wide. How many metres long is the pool?
    I know you will have to find out how long the w is, but how would i do that?
    when we say twice something, we mean two times it. "double" is another word that means 2 times. anyway, if we call the width w, then 2 times w is 2w, so that would be the length.

    solution:
    let w be the width of the pool
    since the length is twice the width, we have:
    length = 2*w = 2w meters
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Member Sazza's Avatar
    Joined
    Apr 2007
    From
    Australia
    Posts
    98
    Okay so i know how to do these like a old hat, with:

    1/2 x 26y
    I'd divide the 2 into 2?

    Like can you outline the basic steps i would take everytime i'd be asked to do this?
    Follow Math Help Forum on Facebook and Google+

  11. #11
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by Sazza View Post
    Okay so i know how to do these like a old hat, with:

    1/2 x 26y
    I'd divide the 2 into 2?

    Like can you outline the basic steps i would take everytime i'd be asked to do this?
    yes. we look for the common factors. we see a 26 in the top and a 2 in the bottom. they have a common factor of 2. so we divide 2 into 2 and get 1, so we replace the 2 with 1, and divide 2 into 26 and get 13, so we replace the 26 with 13. and take it from there
    Follow Math Help Forum on Facebook and Google+

  12. #12
    Member Sazza's Avatar
    Joined
    Apr 2007
    From
    Australia
    Posts
    98
    okay so i have this: since the 26 is a common factor of 2, you divide 2 by 2 and you get 1, so you put 1 and cross out the 2, but the 2 that has just been crossed out you divide that by 26 and you get 13, and since if you punch it into the calculator 2 divided by 26 you getta bunch of numbers so you put itL 26 divided by 2 and you get 13.
    So i understand that, but how would i get the answer to the whole thingo? Would i times the 2 answers i got (13, and 1?) or what??
    Follow Math Help Forum on Facebook and Google+

  13. #13
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by Sazza View Post
    okay so i have this: since the 26 is a common factor of 2, you divide 2 by 2 and you get 1, so you put 1 and cross out the 2, but the 2 that has just been crossed out you divide that by 26 and you get 13, and since if you punch it into the calculator 2 divided by 26 you getta bunch of numbers so you put itL 26 divided by 2 and you get 13.
    So i understand that, but how would i get the answer to the whole thingo? Would i times the 2 answers i got (13, and 1?) or what??
    yes, we would just multiply the tops to get the tops, and multiply the bottoms to get the bottom. so the tops are 1 and 13 and y, 1*13*y = 13y, and the bottoms are 1 and 1 so 1*1 = 1, so the answer is 13y/1 = 13y

    that is,

    1/2 * 26y = 1/1 * 13y = 13y
    Last edited by Jhevon; May 8th 2007 at 10:36 PM.
    Follow Math Help Forum on Facebook and Google+

  14. #14
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    and for the record. i noticed you had problems actually dividing stuff with your calculator, here's how to do it.

    let two numbers be a and b. when we say we want to "divide b into a" or "divide a by b" or we want "a divided by b" we mean:

    a/b = ?

    so if i say, "what is 18 divided by 2" i mean i want to compute 18/2 = ?

    now the way we do that on a calculator is that we always plug in the number we want to divide by last, that is the number at the bottom of the fraction. so we want 18 divided by 2, that means we want 18/2, since 2 is at the bottom of the fraction, we enter that number last. so on a calculator we would:

    step 1: enter the number 18
    step 2: press the division button
    step 3: enter the number 2
    step 4: press "enter" or "ans" or "=" or whatever your calculator uses to compute results
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Multiplication of 2xy^2. (-3x^2. y)
    Posted in the Algebra Forum
    Replies: 1
    Last Post: August 1st 2011, 06:02 PM
  2. [SOLVED] Multiplication
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: February 26th 2011, 10:33 PM
  3. Abstract Algebra: Completing coset Multiplication Tables
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: May 4th 2010, 03:41 AM
  4. Multiplication mod 2
    Posted in the Number Theory Forum
    Replies: 2
    Last Post: February 8th 2010, 10:04 AM
  5. Help on multiplication algebra problem.
    Posted in the Algebra Forum
    Replies: 1
    Last Post: April 9th 2008, 02:14 PM

Search Tags


/mathhelpforum @mathhelpforum