Results 1 to 6 of 6

Thread: percentage calculation wording

  1. #1
    Newbie
    Joined
    May 2017
    From
    Middle East
    Posts
    4

    percentage calculation wording

    Hello Guys, I'm having an issue with percentage calculations, my problem is not with the numbers, it is with what the operation does.

    Here it is:

    if A was increased by 20%, to find the original value of A we divide by 1.2, that is A(original)= A/1.2 .

    So the division is what confuse me, what does it do to get the original value of A. For example if I multiply 6 by 1/7, The result is how many sevens in a 6. Or if I divide 10 over 2 I get 5 (which indicates there are five 2's in a 10).

    Sorry I know it is confusing but I need to understand the concept. I know the maths but I'm missing the wording of the operation.

    I face these sort of questions frequently in Business related material.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    16,043
    Thanks
    3621

    Re: percentage calculation wording

    if A was increased by 20%, to find the original value of A we divide by 1.2, that is A(original)= A/1.2
    that is correct because 120% of $A_0$ is written, $1.20 \cdot A_0 = A \implies \dfrac{A}{1.20} = A_0$


    For example if I multiply 6 by 1/7, The result is how many sevens in a 6.
    No ... multiplying 6 by 1/7 is $\dfrac{6}{1} \cdot \dfrac{1}{7} = \dfrac{6}{7}$

    note there are 42 sevenths in 6.

    $6 \div \dfrac{1}{7} = 6 \times 7 = 42$

    if I divide 10 over 2 I get 5 (which indicates there are five 2's in a 10).
    if you divide 10 by 2 (divide 10 over 2 is incorrect phraseology), you get 5. 10 over 2 is the fraction where division of 10 by 2 is understood.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    May 2017
    From
    Middle East
    Posts
    4

    Re: percentage calculation wording

    Still I didn't understand the meaning of A/1.2 ?? I know that it result [A][/o] .
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    16,043
    Thanks
    3621

    Re: percentage calculation wording

    Quote Originally Posted by Thespark505 View Post
    Still I didn't understand the meaning of A/1.2 ?? I know that it result [A][/o] .
    this is about as simple as I can make it ...

    (100% of original cost) + (20% of original cost) = new cost

    changing the percents to their decimal equivalents ...

    $(1.00)A_0 + (0.20)A_0 = A$

    note the two terms on the left side have $A_0$ in common ...

    $A_0(1.00 + 0.20) = A$

    note that $(1.00+0.20) = 1.2$ represents a multiplier that takes into account the original cost and the 20% mark up

    $A_0(1.2) = A$

    the inverse operation of multiplication is division ... in other words, "undoing" the multiplier to get the original price requires division

    $\dfrac{A_0(1.2)}{1.2} = \dfrac{A}{1.2}$

    $\dfrac{A_0(\cancel{1.2})}{\cancel{1.2}} = \dfrac{A}{1.2}$
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    May 2017
    From
    Middle East
    Posts
    4

    Re: percentage calculation wording

    Wow... thanks for the effort. I know got the idea.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    Joined
    Feb 2015
    From
    Ottawa Ontario
    Posts
    1,645
    Thanks
    308

    Re: percentage calculation wording

    Division is reverse of multiplication:

    5 * 4 = 20 : 20 / 4 = 5

    100 * 1.2 = 120 : 120 / 1.2 = 100
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. percentage calculation
    Posted in the Algebra Forum
    Replies: 3
    Last Post: Sep 11th 2016, 10:06 AM
  2. Simple calculation of difference in percentage
    Posted in the Statistics Forum
    Replies: 2
    Last Post: Jul 30th 2009, 01:34 AM
  3. Help with wording of a question
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: Feb 6th 2009, 08:35 PM
  4. percentage area calculation
    Posted in the Advanced Applied Math Forum
    Replies: 2
    Last Post: Jan 15th 2009, 12:45 AM
  5. Percentage Calculation Problem
    Posted in the Statistics Forum
    Replies: 1
    Last Post: Nov 3rd 2008, 03:32 AM

/mathhelpforum @mathhelpforum