Thread: 1=2!

This is a very well know puzzle, but for those who don't know it...

X=Y
X-Y=0
2X-2Y=0
2X-2Y=X-Y
so..
2(X-Y)=1(X-Y)
2=1 !!

This proves that 2=1. Which is impossible. Who can show where these equations are wrong?

Originally Posted by Corum

This is a very well know puzzle, but for those who don't know it...

X=Y
X-Y=0
2X-2Y=0
2X-2Y=X-Y
so..
2(X-Y)=1(X-Y)
2=1 !!

This proves that 2=1. Which is impossible. Who can show where these equations are wrong?

Dividing by 0 is undefined as pretty much everyone on the forums knows

I should have labeled it pre-playschool puzzle.

see also:
http://www.mathhelpforum.com/math-he...oof-1-2-a.html

for more 'proofs' that show 1=2.