Let's analyze the bar graph provided:

1. Identifying Percentage for Grade B: The graph shows that 40% of students earned a grade of B. Given that the class contains 20 students: $\text{Number of students with a B} = 0.4 \times 20 = 8$ Answer: 8 students earned a B.

2. Finding Students Who Earned a C or Better (Grades A, B, and C):

   • A: 20%
   • B: 40%
   • C: 15%

   Adding these percentages gives: $20\% + 40\% + 15\% = 75\%$ Calculating 75% of 20 students: $0.75 \times 20 = 15$ Answer: 15 students earned a C or better.

Would you like further details on the calculations or have any questions?

Here are some related questions for further practice:

1. If the class size increased to 30 students, how many would have earned a B?
2. What percentage of students earned a grade of D?
3. How many students earned less than a C?
4. If 5 students improved their grades from C to B, how would that change the percentage for each grade?
5. What would be the number of students earning each grade if the class size doubled?

Tip: When working with percentages, always double-check that the total is consistent with the given data to avoid calculation errors.