This is an actual true story.

I went into a store this morning, and made a small purchase.  The total came to $3.58.  I handed the cashier four dollar bills, and then I told her I had eight cents.  She had already rung up the $4 into the machine, and my additional change clearly perplexed her.  She took a moment, doing some quick math in her head, and then she handed me a dime and a penny.

I could have let it go I guess, but I felt that I was well within my right to correct her and not get short changed.  I told her that she owed me fifty cents, and she took back her dime and penny and gave me two quarters, but I could tell she wasn’t really sure.

So here’s my question – how the hell did she get that she owed me 11 cents?  When she first rang it up, the machine said that she owed me 42 cents.  Than I gave her 8.  How does 42 plus 8 equal 11?