Chemistry
posted by Pablo .
I have a Chemistry question which should be very simple but I do not know what significant figures are.
Assuming the following numbers are measurements and using the rules for significant figures, determine the answer for the following calculation.
(15.5/42)*219.5=
1. 81.0059
2. 81.006
3. 81.01
4. 81.0
5. 81
The number obtained from the calculator is 81.00595238 should I just round or are significant figures something else entirely?

Here is a good site to read about s.f.
http://www.chemteam.info/SigFigs/SigFigs.html
15.5 has 3 s.f.
42 has 2 s.f.
219.5 has 4 s.f.
This is a multiplication/division problem.
So the answer may have no more than xxxx s.f.; therefore, the answer is xxxxx. 
Thanks a lot!