About 20 years ago, I was standing in the checkout line at a cafeteria-style restaurant. Everyone in line was over the age of 30 because that style restaurant mainly appealed to the older generation. The checkout clerk, who was probably in her early twenties, rang up the man in front of me, and he handed her a 20 dollar bill. She punched in the 20.00 and hit return. Just at that instant, the electricity flickered. The cash register momentarily went dead and then came back on, but the transaction was lost. The clerk didn't know what to do. At first the people in line thought she wasn't sure if the transaction had been recorded or if she needed to repeat it, but that wasn't the problem. She didn't know how much change to give him. She remembered the price of his meal. She knew he had handed her $20. She couldn't tell what the change should be unless the cash register told her. Everyone in line knew exactly what the change should be, but she couldn't risk taking our word for it. A succession of managers was called to the scene until they found someone old enough to know how to make change for a twenty without electronic aid. Until yesterday that was my "young people don't know how to make change" story.

Yesterday, I was at the cash register paying for an item that cost $7.42. I reached into my purse, grabbed a ten-dollar bill and then poked around in my change pocket. I pulled out a quarter, a nickel, a dime and two pennies. I dropped the change into the palm of the checkout girl and then handed over the bill. She set the bill aside, spread the coins across her palm and stared at them for 20 seconds or so. She stared for so long, I began to worry: Had I grabbed a third penny instead of the dime I was aiming for? Is she trying to find a tactful way to tell me I've given her the wrong amount? Finally she looked up, held out the coins and asked, "Is this 42 cents?"

My first thought was: what in the world would have happened if she had needed to give ME 42 cents in change? If she can't count out 42 cents, what would she have done? Grabbed random coins, and if I complained add more random coins? Call a manager? I wondered how she had been handling this problem up to now, but then I realized: I may have been the very first customer she has ever had that paid for something in cash.

We are rapidly becoming a cash-less society and as we do, the ability to count change is becoming obsolete. Money-counting lessons will eventually be dropped from the school curriculum, and my question is: Will this have unintended repercussions?

I frequently have this exchange with my students:

Student: (staring at 75 ÷ 25)

Me: How many quarters are in 75 cents?

Student: Oh. Right. Duh. (writes 3)

Coinage is an excellent medium for practicing all sorts of math skills that have applications in other places, but how many of those applications will continue to be relevant? Do we need to be able to do things like divide 75 by 25 in our heads? Much of the math in the current high school curriculum is unnecessary for the vast majority of adults. We teach it anyway because we want to leave the door open for our students to choose those careers that need math. However, there are other things going on when we study math. What we learn shapes our brains. For a long time we justified teaching geometry proofs by telling students that proof by deduction teaches us "how to think." Geometry proofs have largely been dropped from the Common Core curriculum. (You can read my elegy here.)

Will we see changes for the worse in students' overall cognitive functioning? Will becoming a cash-less society have an adverse effect on our brains?

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