1
$\begingroup$

Say, for example, $50.0-49.6=0.4$. Does this result have $1$ significant figure, or $3$ (as in the data: $50.0$ and $49.6$)?

Had it been $50.0-4.6$, it is understood that the answer is $45.4$, by the rules of significant figures. How do I apply them in the "$50.0-49.6$" case?


This question deals with $50-49.6$; so a related but not the same question.

$\endgroup$
  • 1
    $\begingroup$ This might help: chemistry.stackexchange.com/a/74496/43942 $\endgroup$ – Berry Holmes May 20 '17 at 3:43
  • $\begingroup$ Had checked that already. It justifies the rules-of-significant-digits[-specially-concerned-about-addition], So, doesn't answer my query; at least, I don't see it, if it does. $\endgroup$ – digikar May 20 '17 at 4:19
4
$\begingroup$

There's an easy way to look at this.

Lets say the value $50.0$ refers to $\pu{50.0 cm}$ measured accurately to $\pu{0.1 cm}$, and that $49.6$ refers to $\pu{49.6 cm}$ measured accurately to $\pu{0.1 cm}$. The difference would be, as you've said, $\pu{0.4 cm}$ measured to $\pu{0.1 cm}$ accuracy.

So, yes, the answer has only one significant digit.

Your initial measurements aren't more accurate than $0.1$, so adding two extra significant digits is incorrect.

I hope this helps.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.