Answer: Average if 9 courses is 40.
Explanation:
Since we have given that
Number of courses = 4
Average of 4 courses = 90
We need to find the average of 9 courses.
Let the average of 9 courses be x.
According to the question, we get that
4 × 90 = 9 × x
360 = 9x
x = 360 ÷ 9
x = 40
Hence, average if 9 courses is 40.