1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Linear Algerbra Equation help Thanks

  1. Jun 30, 2011 #1
    Linear Algerbra Equation help :) Thanks

    1. The problem statement, all variables and given/known data

    Problem 20. Solve for x :
    1.25x − 6 = x

    1.25x −x = 6

    (1.25 − 1)x = 6 On combining the like terms
    on the left.
    .25 x = 6

    x = 24. On multiplying both sides
    by 4.

    2. Relevant equations



    3. The attempt at a solution

    Well i know x = 24. but how does 1.25 0- 1 = .25? how do i get 24x? why do i multiply both sides and why did i multiply them by 4?

    My attempt
    Problem 20. Solve for x :
    1.25x − 6 = x

    (1.25-x)
    (1.25-1(x) = 6
    1.24x = 6
    (1.24 = 6 is 1.24 x 6 so i divide right?)
    20.0x(rounded the nearest 10th..i think)

    20.0x = x
    x = 20.0x
     
  2. jcsd
  3. Jun 30, 2011 #2
    Re: Linear Algerbra Equation help :) Thanks

    1.25x - 1x = ? (it's not 1.24)
     
  4. Jun 30, 2011 #3
    Re: Linear Algerbra Equation help :) Thanks

    This is not Linear Algebra or Physics...

    I don't understand how you got 1.24 from 1.25 - 1 = 0.25??
     
  5. Jun 30, 2011 #4
    Re: Linear Algerbra Equation help :) Thanks

    put 1.25 - 1 into your calculator and you will see that 1.25 - 1 = .25
     
  6. Jun 30, 2011 #5

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: Linear Algerbra Equation help :) Thanks

    The OP's problem is he didn't learn how to add and subtract decimals properly in grade school. The OP is ignoring the decimal in 1.25 and is making the subtraction as if it were a multiplication instead, where you do the multiplication on the numbers first and then insert the decimal afterwards.

    The OP says: 1.25 - 1 is the same as 125 - 1 = 124 and then places the decimal as original: 124 becomes 1.24 just like
    1.25 * 2 is the same as 125 * 2 = 250, put in the decimal and 1.25 * 2 = 2.50
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook