Final answer:
The interval "21 to 30" contains less than 1/5 of the values in the data set.
Step-by-step explanation:
To determine which interval contains less than 1/5 of the values, we need to calculate 1/5 of the total number of values. 1/5 of 25 values is 25/5 = 5. Among the given intervals, the interval "21 to 30" has a frequency of 3, which is less than 5. So, the interval "21 to 30" contains less than 1/5 of the values in the data set.