atomic_fungus (atomic_fungus) wrote,

#603: Rounding errors

I figured it out.

Here in entry 594 I wondered how $0.18 was 10% of $1.50, but I looked at the receipt again.

It's not 10% of $1.50. It's 10% of $0.25 six times.

Why does that matter?

Because the cash register rounds fractional pennies up. 10% of 25 is 2.5, and the cash register rounds it up to 3.0...and 6 times $0.03 is $0.18, which is actually 12% of $1.50.

I always assumed that the thing took off 10% of the pre-tax total, not 10% off of each unit. That's pretty cool. But even so you can really only game the system when it comes to buying a number of items with a two-digit price, and it really only works well if the ones digit is five or less.

Another thing most people wouldn't care about, and wouldn't bother to figure out if they did.

  • #8640: INCORRECT

    Seeing the title of Friday night's ST:TOS ep ("The Changeling") reminded me of one of my pet peeves. In DS9, Odo is the station security chief. He's…

  • #8639: Well, Star Trek...

    Last night I watched ST:TOS, ST:TNG, and ST:DS9 on H&I. I did it again tonight. DS9 in particular--they've gotten to the big war, to the time when…

  • #8638: Rental Girlfriend

    ...Mami must be destroyed. She's just plain evil. That's all there is to it. I don't think I have ever hated a character quite as much as I hate…

  • Post a new comment


    default userpic

    Your reply will be screened

    Your IP address will be recorded 

    When you submit the form an invisible reCAPTCHA check will be performed.
    You must follow the Privacy Policy and Google Terms of use.