It takes one guy 2 hours to wash 1 car. it takes another guy 4 hours to wash the same car. how long for them to wash two of the same cars

This is a difficultly worded question- is it asking for how long it takes for the first guy to wash two cars and separately how long it takes for the second guy to wash two cars? If so, the answer is 4 and 8. If it's asking how long it takes them to band together and wash 2 cars, it will take 4 hours.

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.