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At a certain food stand, the price of each apple is ¢ 40 and the price of each orange is ¢ 60.Mary selects a total of 10 apples and oranges from the food stand, and the average (arithmetic mean) price of the 10 pieces of fruit is ¢ 56.How many oranges must Mary put back so that the average price of the pieces of fruit that she keeps is ¢ 52?
A.1 B.2 C.3 D.4 E.5 这题答案是E,我选了B,实在是算不出5来! |
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