Always use significant figure rules. remember that these rules apply to all numbers that are measurements. a person walks along a road 3.0 miles and rests. then taking another road, he travels 5.00 miles; and switching to a dirt path, he walks 4.000 miles before arriving at his destination. how far has he traveled?

To find the total number of miles traveled by a person, we add the distance that he has traveled: 3.0 + 5.00 + 4.000. 

Now, to find the accurate number of significant figures when adding measurements, the basic rule for addition is to use the least number of decimal places when reporting the result.

Now, since 3.0 has the least number of decimal places, we report the sum with 1 decimal place and have 12.0 miles as the total distance traveled by the person to reach his destination.

 12.0 miles

Divide 108.2 x 10^6 into 1.5 x 10 and the result will be in au (astronomical units)