In Mrs. Marsh's algebra class, 30 of the 36 students took the Chapter 4 test, and their mean score was $72 \%$. The next day the other six students took the test and their mean score was $78 \%$. What is the new class mean? Express your answer as a percent.
If 30 students had an average of 72, then their total points were 30 x 72 = 2160.
If 6 students had an average of 78, then their total points were 6 x 78 = 468.
Adding the points of both groups: 2160 + 468 = 2628 points
2628 divided by 36 gives an average of 73.
As an percentage, it is 73%.