## Puzzle Details

A Proof That 2 = 1:

1. X = Y let x=y

2. X*X = XY multiply by x on both sides

3. X*X - Y*Y = XY - Y*Y subtract y*y from both sides

4. (X+Y)(X-Y) = Y(X-Y) factorise

5. (X+Y) = Y divide by (x-y) on both sides

6. Y+Y = Y replace x with y

7. 2Y = Y factorise

8. 2 = 1 divide by y on both sides

Where lies the flaw in the logic?

**Answer:**On line 4 we are dividing both sides by (X-Y), now, since X=Y, this is 0. We are not allowed to divide by zero. This leads to a meaningless conclusion.

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