# Question #31cbf

Jan 5, 2015

When rounding, you only look at the decimal right behind the one you'll be rounding to.

If this is 5 or more, you round up , otherwise you just cut off (or round down, which is the same).

$\frac{3 \pi}{4} = 2.35610 \ldots$ 3d decimal is $6$ so you round up : $2.36$

$\frac{7 \pi}{4} = 5.4977 \ldots$ 3d decimal is $7$ so again up : $5.50$

Common mistake: Rounding in steps.
Task : Round $5.489$ to a whole number
3rd decimal is 9 so the 8 before is is rounded up to 9
2th decimal is now 9, so 3th decimal is rounded up to 5
1st decimal is now 5, the answer is $6$
WRONG!
If you want a whole number, as in this case, you only look at the first decimal, which is 4, so the right answer is $5$
(Even 5.4999999 would be rounded to 5)