...perhaps he can learn something.

Youngsters today never learn how to do this because they have pocket calculators, so they brute-force everything and come out with numbers, but they can't just look at them and realize they are totally unrealistic if they made a mistake somewhere in the calculation.

We had to learn to do this to separate the powers of ten from the numbers. The former could be done in your head, the latter you could approximate mentally, and then calculate directly with a slide rule to 3 sigdits. And the dimensional analysis let you know if you had the setup right. It eliminated a lot of obvious errors right from the start. If you calculated the number of grams of precipitate in a chemistry lab problem and it came to 10^29 square meters, you knew immediately you'd probably made a mistake.

This isn't hard, I learned how to do it in high school chemistry, and I went to a little redneck high school in rural Florida. And it served me well for the rest of my academic and professional life.