Significant Figures

[Scafalon40]

A question has two parts: (a) and (b)
The answer in (a) is required in (b)
In part (a) after doing the calculation I give my answer to two significant figures, the actual one being 6 or 7 significant figures long
In part (b) I have to use the answer in (a)
Whether I use the 2 significant answer or the 7 one in my calculation, my final answer is still correct

Now this is where the problem lies: In math I have clearly been instructed not to use a rounded off form of the answer in (a) in the calculation in (b) because that will result in error in the final result
But in Chemistry and Physics calculations the final answer is still correct no matter how may numbers of significant figures i use from the answer in (a) in part(b)
Even in the marking schemes they have used rounded off answers of (a) in (b)
My question: should i use my full calculator display throughout or use the rounded off answer of (a) in (b) in Chemistry and Physics papers?
I hope that wasn't too complicated!

 

[johnsth]

my advice would be to use full calculator display

 

[Scafalon40]

my advice would be to use full calculator display

Yeah, I thought so too.

 

[johnsth]

seems like i was the only one to answer...u could have atleast like it...LOL just kiddin....its no pressure

 

[Scafalon40]

seems like i was the only one to answer...u could have atleast like it...LOL just kiddin....its no pressure

Happy?

 

[johnsth]

Happy?

haha.....thnx.....but i wasn't giving u pressure right? i hope u wrote that "happy" in a good way

 

[Scafalon40]

haha.....thnx.....but i wasn't giving u pressure right? i hope u wrote that "happy" in a good way

Of course I did!

 

[MindStealth]

In most cases you can just round of the value of part (a) to whatever figures you want and then in part (b), just write the value you will be using from part (a) in the start but as a fraction. I'll give you an example:

(a) velocity = d/t
= 100/3
= 33.3 <---- ANS
(b) velocity = 100/3
acceleration = v/t
= (100/3)/3
= 11.1 <----- ANS
I can't explain it in a better way. If you have the natural display series of casio (ex. fx-991ES), it will always give you the answer in fraction form, just use it when the equations are complex.

 

[Scafalon40]

In most cases you can just round of the value of part (a) to whatever figures you want and then in part (b), just write the value you will be using from part (a) in the start but as a fraction. I'll give you an example:

(a) velocity = d/t
= 100/3
= 33.3 <---- ANS
(b) velocity = 100/3
acceleration = v/t
= (100/3)/3
= 11.1 <----- ANS
I can't explain it in a better way. If you have the natural display series of casio (ex. fx-991ES), it will always give you the answer in fraction form, just use it when the equations are complex.

I do have the Casio fx-991 ES calculator and I have been using this fraction technique you just described with it for a long time now, that was not my question
I want to know weather the examiners will penalise me not if I don't use rounded off versions of the answers, as they have in their marking schemes

 

[MindStealth]

I do have the Casio fx-991 ES calculator and I have been using this fraction technique you just described with it for a long time now, that was not my question
I want to know weather the examiners will penalise me not if I don't use rounded off versions of the answers, as they have in their marking schemes

Well the examiners will probably cut marks if your approximation give a change in the answer.

 

[Scafalon40]

Well the examiners will probably cut marks if your approximation give a change in the answer.

So I'll just use the full calculator display...
Problem resolved.
I thank everyone who participated(even though it was only two members!)

 

[Nikesh]

A question has two parts: (a) and (b)
The answer in (a) is required in (b)
In part (a) after doing the calculation I give my answer to two significant figures, the actual one being 6 or 7 significant figures long
In part (b) I have to use the answer in (a)
Whether I use the 2 significant answer or the 7 one in my calculation, my final answer is still correct

Now this is where the problem lies: In math I have clearly been instructed not to use a rounded off form of the answer in (a) in the calculation in (b) because that will result in error in the final result
But in Chemistry and Physics calculations the final answer is still correct no matter how may numbers of significant figures i use from the answer in (a) in part(b)
Even in the marking schemes they have used rounded off answers of (a) in (b)
My question: should i use my full calculator display throughout or use the rounded off answer of (a) in (b) in Chemistry and Physics papers?
I hope that wasn't too complicated!

Better use your original values (apart from round off value), coz this will lead your answer to accuracy.
if you use round off value, there is less chance of getting accuracy mark for your answer. However in some cases such answers are too given marks.
Your round off values are just to satisfy the significant numbers, they are in actuality of no use in further calculations.