Answer :

To convert kilometers to meters you multiply it by 1000 so it's equivalent to 6000 meters. Then you need to convert the centimeters so you divide that by 100 so it's equivalent to 6 meters. To convert millimeters you divide by 1000 so it's equivalent to 6 meters. Compare all the numbers: 6000, 60, 6, 6. The kilometers is the greatest.
iGreen
Convert all of them to meters.

1 km = 1000 meters

6 * 1000 = 6000

6 km = 6000 m

1 cm = 0.01 m

600 * 0.01 = 6

600 cm = 6 m

1 mm = 0.001 m

6000 * 0.001 = 6 m

So we have:

6000 m, 60 m, 6 m, and 6 m.

So 6 kilometers is the greatest.