The numbers of hours worked (per week) by 400 statistics students are shown below. ​ The cumulative percent frequency for < 29 hours is

A) 50.
B) 75.
C) 200.
D) 300.

To find the cumulative percent frequency for < 29 hours, we need to add up the percent frequencies for all values less than 29. From the cumulative frequency table, we can see that the percent frequency for the interval 0-9 is 3.25, for 10-19 it is 8.5, for 20-29 it is 13.5. Adding these gives:
3.25 + 8.5 + 13.5 = 25.25%
Therefore, the cumulative percent frequency for < 29 hours is 25.25%.
The closest answer choice is B) 75 which is the complement of the cumulative percent frequency for ≥ 29 hours:
100% - 25.25% = 74.75%, which is approximately 75%.