From the given information, the total amount of marks obtained by the class is   $$20(80)+8(90)+2(100)=2520.$$Therefore, the class average is  $$\frac{2520}{30} = \boxed{84}.$$
Question:
A class of 30 students recently took a test.  If 20 students scored 80, 8 students scored 90, and 2 students scored 100, then what was the class average (the mean) on this test?
Answer:
Let's think step by step.

user
84
A class of 30 students recently took a test.  If 20 students scored 80, 8 students scored 90, and 2 students scored 100, then what was the class average (the mean) on this test?
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