A Bus Left MSP with 50% Off

On the bus ride home last night, a young nurse (with a gaudy black ring on her engagement finger) talked about getting married. They registered at Marshall Fields and the China pattern they liked was marked down to 50%. Since she got 15% off anything she purchased while registering and another 15% off if she opened a Marshall Fields charge card, they decided to just buy the China themselves and register for other things. (“Nobody else would get that kind of deal.”) It was normally $140/place setting, but she was amazed to have paid a paltry $40/place setting.

That got me wondering: were both of the 15% discounts applied to the original price ($140) or the already-discounted-50% off price ($70)? After doing math the rest of the bus trip home, I realized she got a discount of about 72%.... meaning that one of the 15% discounts was applied to the regular price and one was applied to the already-discounted price. That was an answer I wasn't expecting. Just goes to show how fun math can be.