Significant figures question

[JaidynM]

I just have a quick question on significant figures; I had a look through a couple of threads (including the sig figs guide) and couldn't find an answer.

Say for a question, the least accurate piece of data is given to 2 significant figures. The question has multiple parts, a), b), c) etc. During your working out (for example, in part a) if you're finding the mol in order to work out the concentration) do you write done all of your calculations to 2 significant figures or can you use 3 or 4 and then write your answer in 2 significant figures?

Also, would you write your answer to each individual part to 2 significant figures or could you write the answers to all of the questions excluding the final part (say part c) correct to 3 or 4 significant figures and then write your answer to part c) (the final part) to 2?

Finally, I've heard that every year there's only a single question to which this applies; what's that about?

[Spxtcs]

I just have a quick question on significant figures; I had a look through a couple of threads (including the sig figs guide) and couldn't find an answer.

Say for a question, the least accurate piece of data is given to 2 significant figures. The question has multiple parts, a), b), c) etc. During your working out (for example, in part a) if you're finding the mol in order to work out the concentration) do you write done all of your calculations to 2 significant figures or can you use 3 or 4 and then write your answer in 2 significant figures?

Also, would you write your answer to each individual part to 2 significant figures or could you write the answers to all of the questions excluding the final part (say part c) correct to 3 or 4 significant figures and then write your answer to part c) (the final part) to 2?

Finally, I've heard that every year there's only a single question to which this applies; what's that about?

from my experience I think it's best to work through the calculations using as many (3 or 4) sig figs and then state the final answer to that part at the end of it (e.g. part a), because if you show the calculations to 2 sig figs, even though you might use 3 or 4 in your actual calculator, the answer isn't necessarily the same (a difference of 1 or 2 sig figs can change the answer quite a lot even though you may not think). so in that respect, you could lose marks (i.e. on sacs, exam) for your working out not matching the correct answer which you will get by using 3 or 4 sig figs in your calculator (if that makes sense)

in exams there might be a specific question worth like 1 mark asking 'how many significant figures should this student use to calculate the mass of....' but nearly every question needs proper use of sig figs, otherwise like I said, you can lose easy marks!

[JaidynM]

Ahh that makes sense, cheers!