Slide rules still work.

There are good reasons to prefer calculators to slide rules if you're using the tools for production. I get that. There are good reasons to prefer cars to horses if you're using them for transportation, or word processors to pencils if writing a novel. Pencils and horses and slide rules all still work, as good as ever.

Why on Earth would a child use a slide rule?


They're too hard!

No, but they do require some more work, some number sense, on the part of the student. You cannot use a slide rule well if you do not what numbers mean. And many of my students do not.

Slide rules force the user to approximate numbers, to grasp significant figures, to sense numbers.

They're not accurate!

Well, um, yes, they are. Perhaps not as precise, but precise enough to get folks across the ocean in jet planes.

Calculators give shiny numbers with all kinds of digits--the answers look smart and sophisticated.

2 divided by 7 is 0.2857142, according to my calculator, 0.29 according to my slide rule, or more accurately (if not more precisely) 0.3 if I give a fig about sig figs.

With calculators, kids do not get that "2.000" means something different than "2." They might not get that with a slide rule, either, but there's no place to hide.

They need to know how to use calculators "in real life."

How long, really, does it take to master the functions available on a calculator? Functions that look impressive, but are incomprehensible to most students I work with.

(Yes, I know they can "do" problems with them, but with enough time and enough treats, I could teach a pigeon to punch in the right steps...)

I truly believe calculators should be banned in public school. Let children use abaci in elementary school, then slide rules in high school.

Obviously a child who needs to use the tool should be allowed to use it.
Just don't pretend any real understanding is happening.