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

[kthouz]

Let say that a+b=c
this can be writtem as
4a-3a+4b-3b=4c-3c
by arranging
4a+4b-4c=3a+3b-3c
taking out the constants
4*(a+b-c)=3*(a+b-c)
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.

 

[CRGreathouse]

You divide by zero in the last step.

 

[exk]

what he said ^

 

[rock.freak667]

4*(a+b-c)=3*(a+b-c)
So 4=3

You can't divide by a+b-c since a+b=c (i.e. a+b-c=0)...

 

[kthouz]

Cool! you got it!
the trick was to know that dividing by zero is impossible.

 

[ajsingh]

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"

 

[gravenewworld]

Let say that a+b=c
this can be writtem as
4a-3a+4b-3b=4c-3c
by arranging
4a+4b-4c=3a+3b-3c
taking out the constants
4*(a+b-c)=3*(a+b-c)
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.

This is exactly why you never ever divide by a variable. It is horrendous algebra.


x^2=4x


What is x?

75% of students will divide by x and say x=4.

 

[Poop-Loops]

Well they're half-right.

 

[rock.freak667]

This is exactly why you never ever divide by a variable. It is horrendous algebra.


x^2=4x


What is x?

75% of students will divide by x and say x=4.

Then those 75% should always remember that you can only divide by something only if it is not equal to zero!