sig figs

[amar]

When there are sub parts to questions (for example: 1a, 1b etc), do we consider the number of significant figures to clip our answers to from the data given up until that point, all the data in the question (including numbers that are in sub-parts after the question being answered) or only the figures in the 'main body' of the question.

[amar]

good question

[amar]

I agree someone should answer it.

[Lighties]

I would think that you clip them to all the data given until that point, that you are using to work out your solution.

Not entirely sure on that, though.

[jimmy999]

Say you work through your answer using 5 decimal places, and the answer wants 3 significant figures so lets assume that goes to only 2 decimal places, then your entire working out for all parts of the question should use 5 decimal places, and whenever you get to an answer, you put it to 3 significant figures. That way your answer will stay accurate because sometimes cutting down to significant figures too early can alter your result greatly

[jayfan]

Say you work through your answer using 5 decimal places, and the answer wants 3 significant figures so lets assume that goes to only 2 decimal places, then your entire working out for all parts of the question should use 5 decimal places, and whenever you get to an answer, you put it to 3 significant figures. That way your answer will stay accurate because sometimes cutting down to significant figures too early can alter your result greatly

im assuming jimmy999 is suggesting keeping your results in your calculator all the way through, but only writing down answers correct to 3 sig figs

my teacher says the opposite of that - we are taught to round off to the number of significant figures of the least accurate data used in a calculation at the end of THAT calculation. this means you round off each step, and then use that rounded off answer in your next step.

i think this reasoning makes sense in the real world, because when you are doing experiments, your results can only be as accurate as your least accurate apparatus, which would THEN influence all your subsequent calculations. -- i.e. there's no point in keeping your results in your calculator even though it would be more "mathematically" correct

[longy1991]

do not round off your answer in calculations, only in the answer, otherwise you could get the wrong answer. This happens often in physics, chem and all maths. Kids do lose marks because of rounding too early.
It says this in one of the VCAA reports by the way (but that might have been a methods one)

[superflya]

do not round off your answer in calculations, only in the answer, otherwise you could get the wrong answer. This happens often in physics, chem and all maths. Kids do lose marks because of rounding too early.
It says this in one of the VCAA reports by the way (but that might have been a methods one)

+1

[kenhung123]

good question

I agree someone should answer it.

Errr??

[the.watchman]

Lolwut?

[kenhung123]

His talking to himself?

[brightsky]

lolz..