>>>>>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.
>>>
>>>Ok, a couple examples to make sure I understand:
>>>
>>>

>>> 4.008 * 2.09 ------> 4 * 2
>>>38.002 * 0.49 ------> 38 * .5
>>>61.203 * 0.42 ------> 61 * .4
>>> 0.98  * 7.61 ------> 1 * 8 (not sure about the 0.98 going to 1 on this one)
>>>

>>
>>For quick estimates, just keep ONE significant digit. Convert all non-zero digits except the first to zero; if the digit dropped is 5 or more, increase the first digit by one (for rounding). The first example is correct, the second, I would change to 40 * 0.5 (notice the rounding); the third, to 60 * 0.4.
>>
>>The fourth example, once again, is correct: rounding to 1 s.d. means, in this case, rounding to the closest 0.1; 0.98 is closer to 1.0 than to 0.9. Or just look at the algorithm in the previos paragraph (the 8 is dropped, 0.9 is increased to 1.0).
>
>Whew!
>
>Ok, how did the 38.002 become 40 instead of 39? So, DIGIT is the key, not like whole number? But, isn't 40 comprised of two digits of 4 and 0?

The idea is NOT to round to the nearest whole number, but to round in such a way, that you keep one s.d.

In 38.002:

The first significant digit (the first non-zero digit) is 3 - keep it.

Discard all other digits: 38.000 or 38.

Since the first digit dropped is >= 5, add one to the digit you keep; 30 becomes 40.

In step 1, the reason I said "the first non-zero digit" instead of "the first digit" is because some numbers do, indeed, start with zero. 0.072 should be rounded to 0.07, for example.

>How can this be at the 5th grade level?!

I think this should be relatively easy to grasp, once you go through all the steps with a few examples.

Adults to sometimes have trouble with some school math, especially if they slept in their math classes <g> or simply never had a need to apply certain knowledge in practice.

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)