You don’t have to be a math whiz to know that 4 - 2 + 1 equals 3. Yet I was working with several students recently who said it equals 1. And it wasn’t their fault. Nor was it their teacher’s fault.

“That’s just bad math,” my physics professor told me as I struggled to finalize a lengthy equation for calculating potential energy in one of our laboratory experiments. “Use PEMDAS,” she chirped at ...