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

4=3 True or False? Check it out and guess where's the mistake!

  1. May 2, 2008 #1
    Let say that a+b=c
    this can be writtem as
    by arranging
    taking out the constants
    So 4=3

    The mistake is that .... I'll post it soon. i read this from a notebook of my little brother and i firstly agreed to it but by the time i found out why not! Test your knowledge too.
  2. jcsd
  3. May 2, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    You divide by zero in the last step.
    Last edited: May 2, 2008
  4. May 2, 2008 #3


    User Avatar

    what he said ^
  5. May 2, 2008 #4


    User Avatar
    Homework Helper

    You can't divide by a+b-c since a+b=c (i.e. a+b-c=0)....
  6. May 4, 2008 #5
    Cool! you got it!
    the trick was to know that dividing by zero is impossible.
    Last edited: May 4, 2008
  7. May 4, 2008 #6
    I remember my dad showed it to me when I was in 5th or 6t grade. It stumped me, and I showed it to my Math teacher at school who explained the 11th Commandment to me: "You shall never divide by Zero"
  8. May 4, 2008 #7
    This is exactly why you never ever divide by a variable. It is horrendous algebra.


    What is x?

    75% of students will divide by x and say x=4.
  9. May 4, 2008 #8
    Well they're half-right.
  10. May 4, 2008 #9


    User Avatar
    Homework Helper

    Then those 75% should always remember that you can only divide by something only if it is not equal to zero!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook