Rounding Rule for 5

[Michelle Pham_3H]

Hi! I'm still trying to wrap my head around why we were told to round to the nearest even number when the number immediately after the last significant figure is 5. In my high school chemistry class this was never discussed, not to say that high school chemistry is that advanced, but this is still a little mind boggling to me. For example, 0.125 would become 0.12 if I were to round to two significant figures. What exactly would be the rounding error that occurs if I were to round to 0.13 or if I were to round up over many calculations?

[Curtis Wong 2D]

The reason why we round to the nearest even number is because many different people have different ideas about rounding for numbers ending in 5. For some people, it means rounding down, for others it means rounding up. So to clear away the confusion, we just round to the nearest even number to make things easier.

[isauramora3K]

I would say that the rounding error that would occur would be very minimal but if you want to avoid significant errors over many calculations round significant figures at your final answer only.

[Karan Singh Lecture 3]

This is done to avoid rounding errors, by telling everyone on how a number ending in a five should be rounded off to the closest even number. It makes calculations much more simple when everyone does round in the same manner.

[Michelle Pham_3H]

Thanks everyone!

[DAllaf]

Hi Michelle,

I was also initially confused about this weird rounding rule, but I found it the reason that rule exists is because some people are taught to round down and some people are taught to round up when the number ends in 5. My advice would be to wait to rounding till the end of your problem solving and then round to the nearest even number when writing your answer.