Re: A weighty subject

[Leigh Palmer <palmer@SFU.CA>]

> Arlyn DeBruyckere wrote:
>
> > It is also a problem in teaching them about significant figures that 40 Lb
> > (1 sig fig) can be equal to 18.1 Kg (3 sig figs). They don't understand
> > why I get upset when they measure 20 ml and then decide to record 20.00 ml
> > because I told them they should measure to the nearest .01 ml.
>
> I would have said that the value 40 pounds is precise to 2 sigfig. Not all
> final zeros are insignificant; it depends on the context.

I agree. I'd sure complain loudly if I bought a 40 pound bag
of potatoes and found on weighing it that I'd got 36.5 pounds.
The implied contents is net, and it should be *at least* 40.0
pounds. This particular example also demonstrates the shallow
nature of the "significant figure" idea. Surely Arlyn wouldn't
tell his students that the "correct" label should read 20 kg.

Leigh