Date: Wed, 12 Oct 2011 15:42:25
Author: Paul Nord
Subject: Re: Excellent use of significant digits
Total Calorie calculation:
10 +/- 1 Cal
8 +/- 1 OZ
20 +/- 1 OZ/Bottle
20 * ( 10 / 8) = 25 Cal/Bottle
Propagating the errors for that gives 25 +/- 4 Cal per bottle. I'd call that one significant digit. Round the 5 even (or truncate) and a bottle has 20 Calories.
You could claim that the 8 should really have an error of 0.5. But that still gives you an error on the final answer of 3 Cal. 20 Calories is still a perfectly reasonable way to write down that result.
On Oct 12, 2011, at 2:20 PM, Jerry DiMarco wrote:
> At 10/12/2011 01:59 PM, you wrote:
>> This one has great potential for teaching about significant digits.
> But not for basic math, as the calorie tally shows. Wonder how many bottles went out before they discovered that mistake?
> Jerry D