If a rubber band weighs 40 milligrams, how many of them will weigh one kilogram?

To solve this problem, you have to bridge the enormous gap between a milligram and a kilogram. The key lies in the metric system's prefixes. The prefix "kilo-" means one thousand, so one kilogram is equal to 1,000 grams. At the other end of the scale, the prefix "milli-" means one-thousandth, which tells us that one gram is equal to 1,000 milligrams.

By combining these conversions, we can find out how many milligrams are in one kilogram. Since there are 1,000 grams in a kilogram and 1,000 milligrams in each of those grams, you multiply them together (1,000 x 1,000) to find that there are a staggering one million milligrams in a single kilogram.

With all our units aligned, the final step is a simple division. Dividing the 1,000,000 milligrams in a kilogram by the 40-milligram weight of one rubber band gives you the total number needed. For perspective, a 40-milligram rubber band is incredibly light; a common office rubber band weighs over a gram. This tiny weight is closer to that of an orthodontic elastic, illustrating just how many it would take to equal the mass of a bag of sugar.