I was at a church picnic last summer....the youth group (junior high school kids) were selling hotdogs and sodas....the kid couldn’t make change for a $10-bill...I don’t think calculus is the problem...
Even cashiers at the grocery store are no better.
only the older ones get it when I hand them enough change to get only quarters back.
If I buy something that costs $4.79, I'll give them four pennies with a $20 and the confused looks on the kids faces tell it all.