Let's say I want to round the number 3.549 off to two significant figures. Do I have to round the 4 to 5 first, or do I just round the 5 (in the one-tenths place) to 5, since the one-hundreths digit is 4? If I do it by the first method, it would be 3.6, while the 2nd method gives 3.5. Which is right? Thanks.