Why does 0.999 equal 1.

"Why does 0.999 equal 1."

 

As written it doesn't!  However, if you mean the 9's go on forever then:

 

Let x = 0.999999...... etc.

  10x = 9.999999..... etc.

 

Subtract the first from the second to get:   9x = 9  or x = 1

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