[fm]

Hi, I need help with this problem, they ask me to express the answer with the appropiate number of significant figures. If anybody could help me and tell me why it is that number of significant figures. thanks!

3.142(6.251/2)^2

[BeepoGirl]

I imagine it would be 3 or 4 significant figures as 4 is what is given to you in the question. Normally I would use 3 as the accuracy would decrease on calculation.

[Jon Harmon]

Hi, I need help with this problem, they ask me to express the answer with the appropiate number of significant figures. If anybody could help me and tell me why it is that number of significant figures. thanks!

3.142(6.251/2)^2

In this case, assuming "2" is a measured number, the answer would only have 1 significant figure (since "2" only has one significant figure). If "2" is a counting number (ie, if it's *exactly* 2), the answer has 4 significant figures (since both 3.142 and 6.251 have 4 significant figures).

We have a post all about significant figures at Active Answers, plus a sample problem for you to test whether you understand them. Hopefully we can *delete me* http://activeanswers.blogspot.com/2009/02/significant-figures-and-scientific.html

[jcwright]

Spot on John Harmon

You have to look for the measured value with the least significant figures.

e.g 2 x 6.596949 = (1 s.f.) as the measured quantity with the least signifacnt figues is used which is 2.

For instance if were using the ideal gas equation rearranged as follows to find volume;

v=nRT/P , you would look for the least number of significant figures of measured values.

For instance, if moles (n) was 3.22 mol, R=8.314 J K mol, T=293.66 K, P=10135 Pa, you would report your answer to (3 s.f.) as n (moles) is made up of 3 significant figures and has the lowest number overall of significant figures.

Hope this helps

[Borek]

Trick is, it is not clear whether 2 is a measured number, or just a coefficient.