The longest bridge in the world is located in china. it is164,800 meters long. another bridge in china is 69,732 meters long. round each length to the nearest ten thousand to find the answer. what is the approximate difference between the lengths of the two bridges?

170,000 meters long 
71,000 meters long
=99000

164,800 rounded to nearest ten thousand is 16,000
69,732 rounded to the nearest ten thousand is70,000. The difference between 160,000 and 70,000 is 16,000-70,000=90,000
Therefore the approximate length between the lengths of the bridges is 90,000 meters.
If you need further explanation, I will be glad to help.