39. Which of the following conversion factors would you use to change 18 kilometers to meters?

1000 m/1 km

1 km/1000 m

100 m/1 km

1 km/100 m

Converting 18 kilometers to meters.

1 kilometer = 1000 meters

I would use 1000m/1km as a conversion factor.

18 kilometers * 1000m/1km = 18 * 1000m = 18,000m

The km unit cancels out because it is both in the numerator and in the denominator.