Christmas Math

Grandpa and Grandma are sending $150 to buy all the kids presents this Christmas.  At our end, we don't know what G&G need and have decided to send them $100 to get something they really like.  You see where I am going.

Source

 
All the love can be handled in a single clearing entry.    Make a phone call.  The high bidder does a $50 transfer on their smartphone. Not only is this cheaper, it's greener.  No cars drive around burning gas and no Christmas card paper is consumed.

On the receiving end, I used to bank the cheque.  Next time we talked, I'd mention the nicest thing I'd bought since then and give them the credit.