The jet airplane flew about 12 kilometers. In this case, we have to use kilometers because that's the proper scale used for the distance traveled by an airplane.
The bucket holds about 6 liters. In this case, the bucket represents a volume, that's why we have to use liters.
Susan's refrigerator has mass of 78 kilograms. Given that it's a refrigerator, it can't weigh 78 grams, that wouldn't be logical.
