As a math teacher, I am pleased to see that the new carry-on rules for air travel [“Airline workers criticize TSA for policy change on small knives,” news story, March 8] will lead many Americans to rediscover how to convert decimals to fractions so that they can determine whether their knife can come on board.

We are told that a knife may accompany us as long as its blade is no longer than 2.36 inches. But this measurement is not available on most rulers, which are typically marked in increments of eighths of an inch or perhaps sixteenths of an inch. (In case you’re wondering, 21 / 4-inch-long or even 25 / 16-inch-long blades are okay, but 23 / 8 inches is unsafe by the new standard.)

One does wonder how much money was spent to determine that 2.36 inches is safe, yet 2.37 inches is not. Of course, 2.36 inches roughly equals six centimeters, but we all know Americans don’t deal well with the metric system.

Ken Pieper, Burke