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In a certain class, x students are 10 years old, and the remaining y students are 11 years old. What is the average (arithmetic mean) age of all students in the class?
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A.$$\frac{x+y}{21}$$
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B.$$\frac{10·x+11·y}{21}$$
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C.$$110·x·\frac{y}{x+y}$$
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D.$$110·x·\frac{y}{x·y}$$
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E.$$\frac{10·x+11·y}{x+y}$$
E显示答案
