A student got an 80% on a test that had 40 questions on it. How many questions did the student get correct?

The student got 32 questions correct.
40 x 0.8 = 32

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.