Answer: 5 classes.
Step-by-step explanation:
You can use the rule to determine the number of classes for a frequency distribution.
The rule says that where
is the number of classes
is the number of the data points
We know that the number of data points is = 20.
Next, we start searching for so that we can get a number 2 to the that is larger that the number of data points.
This suggests that you should use 5 classes.