>She is in 5th grade and this is her homework...
>
>So, what if it were 28.5 * 1.843? Then 28 * 1.8? 29 * 2? What are the rules? What is significant?
For quick rounding, I would keep ONE significant digit in most cases.
28.5 * 1.843 --> 30 * 2
The idea is to keep the first digit in each number, and replace all other digits with zeroes - rounding the next digit up or down, as appropriate.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)