Three classes have 60, 40, and 50 students respectively. Their average marks are 65, 72, and 60. What is the average mark of all 150 students combined?
65.2
Combined average equals total marks divided by total students; multiply each class size by its average to get its total.
Class 1 total: \(60\times 65 = 3900\).
Class 2 total: \(40\times 72 = 2880\).
Class 3 total: \(50\times 60 = 3000\).
Sum of totals: \(3900+2880+3000 = 9780\) marks over \(60+40+50=150\) students.
Combined average: \(\dfrac{9780}{150}=65.2\).
Hence, the average mark of all 150 students combined is 65.2.
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