Mathematically, what is the correct way to write a speed of 100 meters per second?

Per means "divide". So meter per second means meter/second.
Also note that a negative power in the numerator is equivalent to a positive in the denominator.
Example:
1/s = s^-1
1/(s^2) = s^-2

Based on this:
100 meters per seconds can be written as:
100 m/s , or
100 ms^-1

The major difference is that a histogram is only used to plot the frequency of score occurrences in a continuous data set that has been divided into classes, called bins.  bar charts, on the other hand, can be used for a great deal of other types ofvariables  including  ordinal  andnominal  data sets.