Gifted Issues Discussion homepage Forums General Discussion Semi-wonkish question about significant figures

I looked at it...if you are in debt $3.50 and round it to $4.00 then you would have covered your debt...but if you round it to $3.00 you didn't cover your debt.

But rounding up, rounding down...confusing in the negative.

Maybe this is totally wrong mathematically but I have always taken the absolute value, rounded and then put the sign back on. Hence -3.5 rounds to -4. This has always made intuitive sense to me, at least.

I just discovered something shocking, and it made me think of this thread.

I've gone through most of my life under the impression that one inch is approximately 2.54cm.

I've just discovered that one inch is exactly 2.54cm!

Interesting. I always rounded -3.5 to -4.
Rounding -3.5 to -3 seems strange to me because -3.5000 and -3.5001 would round to different numbers, which means you have to look at more digits to decide how to round.

I also thought 1 inch is approximately 2.54 cm!

American rulers have both, but tapes do not. We use rulers in school, and there continues to be teaching of both, though the metric system is rarely used in day to day life. Tapes are used by folks such as surveyors and they do not use metric in the US.

I realize that some folks, such as mechanical engineers, may use metric, but most people do not. There was a huge push to use metric in the mid-1970s. I recall in 4th grade that we had an entire workbook on the metric system. We were told that everyone in the US would use metric by 1977. It was the Feds that were pushing it, but someone didn't stop to think that this would require changing every speed limit and mile marker sign, not to mention every property survey.

You can't really tell from a ruler whether it's an approximation though, since you need 50 inches to make exactly 127 cm, and that's longer than most rulers.

Some information about it here: http://en.wikipedia.org/wiki/Inch