20
300
40,000,000
200 km
24.0
It doesn't need to be rounded. 2.1 km is the same as 2,100 meters. That's already rounded to the nearest meter, the nearest 10 meters, and the nearest 100 meters.
What does 279 round to?
300
300
300
300
347 km to the nearest 100 km is 300 km. since 300 is close to 347
40,000,000
200 km
489 KM
280
As a wild guess, I would say that is is a km.
0.4 km