[問題]天山5-8

[Albert5]

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

[szyang]

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

設APPLE為X個.ORANGE為Y個
X+Y=10
40X+60Y=56*10......得X=2 Y=8
設減少orange為A個
則40*2+60*(8-A)=52*(10-A)
A=5
ans:E

[Albert5]

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