CHEMISTRY COMMUNITY

In class someone asked the question about what to do about sig figs if you have a 5; e.i. 4.465- and you only have 3 sig figs. Normally I was taught you round up but Professor Lavelle mentioned that that is not always the case and I'm not sure I fully understand the concept. Can someone please explain what to do if you are left with a five on the end like that?

Thanks:)

4.465 with 3 sf's would be 4.46. If the last digit is 5, you round to the nearest even number (2.35 with 2 sf would be 2.4, and 2.65 would be 2.6). If the last digit is above 5, you round up (2 sf for 2.36 would be 2.4). If the last digit is below 5, you round down (1 sf for 2.36 is 2).

I believe this rule is to eliminate rounding errors in a multi-step problem (50% is rounded up and 50% is rounded down). However, in order to be as precise as possible you should not round your answer until the very end of the problem.