I guess he had the popular all or nothing philosophy. Most older profs I had gave you nothing if your answer was wrong.
Every time people complained he would bring up some tiny error at NASA that crashed a billion dollar spacecraft or a hotel lobby that collapsed because of bad math and say "a small mistake still gets you in big **it."
Or "if you can't add with a calculator by now, go waste your time in the business school".
“Or “if you can’t add with a calculator by now, go waste your time in the business school”.”
Nobody had calculators when I was in college. We used slide rules.