Date: Wed, 12 Oct 2011 15:42:25

Author: Paul Nord

Subject: Re: Excellent use of significant digits

Post:

Jerry,

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.

Paul

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.
>>
>> http://failblog.files.wordpress.com/2011/10/6456cc3f-222f-45e7-a778-56cc9f38923b.jpg
>> ......
>
> But not for basic math, as the calorie tally shows. Wonder how many bottles went out before they discovered that mistake?
>
> Jerry D
>
>
>
>

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