Physicists have a secret called “units analysis”. By assigning all quantities a unit, they can then check that the final answer results in the required unit. If it does not, then there has been a mistake. Also, a unit is required for physical units to be meaningful. A weight of “100” does not mean much, whereas a weight of 1 billion points is a bit more impactful.

Here is an example of units analysis:

Jean walks 10 miles. It takes Jean 5 hours to walk that distance. To find Jean’s mean speed, we divide distance by time:

speed = distance/time

speed = 10 miles / 5 hours

speed = 2 miles per hour.

Miles per hour is indeed a unit of speed, so the answer could be correct. Conversely, if the answer came out to be hour/mile the answer would clearly be incorrect