[Joisu]

What are significant figures? How can you tell how many significant figures are in a number?

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Indicate the number of significant figures in each of the following:

a) 1422   b) 65,321  c) 1.004 x 10^5  d) 200  e) 200.  f) 2.00 x 10^2   g) 435.662  h) 56.341

My answers: a) 4 (sig figs)  B) 5  c) 6  d) 3 (i don't get it....what's the difference between d and e...?) f) 3    g) 6    h) 5
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and for this one...

12. Evaluate each of the following and write the answer to the appropiate number of sig fig

a) (4.031)(0.08206)(373.1)/(0.995)
b) (12.011)/(6.022 x 10^23)
c) (0.500)(44.02)
d) (0.15)/(280.62)

Is there a special way to multiply or divided them? Or do I just multiply or divided them like I normally would?

[govibe]

for your first question, d) only has one sig fig while e) has three sig figs, due to the inclusion of a period, which increases the certainty...

For your second question, you just divide/multiply like you normally would and you round the number off to the number with the last amount of sig figs

[enahs]

d) only has one sig fig while

An integer number has infinitely many significant figures.

The number 4 does not have 1 significant figure, it has infinitely many. As it is 4.00000 with the zeros never ending.

Same thing for 200, or 65,321, 1422 or 132123278464782648327643278642783678324

[Yggdrasil]

While technically I would agree with enahs, from the context, 200 would have one sig fig.

For example, if someone wrote down 200m or 200g, I would not assume they violated the laws of physics and made a measurement with infinite precision.  However, if one were to talk about something with quantum number 4, then they mean four with infinite precision and not 4±1.  So it depends on the context where you see the number reported.

[enahs]

For example, if someone wrote down 200m or 200g, I would not assume they violated the laws of physics and made a measurement with infinite precision.

True. But then again, if someone said they massed something and just put down "200g" I would say "No you did not.".

And this illustrates the point that when making measurements make sure to read the accuracy (and precision) abilities of your instruments and record them properly.

[DevaDevil]

enahs; you are right that when the number is exact it has infinite sigs, but for the sake of the exercise I would assume none of the numbers given to be exact numbers.


anyway Here is a good tutorial on significant numbers.