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 54¢. How many oranges must Mary put back so that the average price of the pieces of fruit that she keeps is 50¢?
Select the correct option
A) 1
B) 2
C) 3
D) 4
E) 5
If the average price is 54, then Mary has 7 oranges and 3 apples (a ratio of 7:3).   For the average price to be 50, the ratio should be 1:1.   Mary must put back 4 oranges.   The answer is 4.
<result>D</result>
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 54¢. How many oranges must Mary put back so that the average price of the pieces of fruit that she keeps is 50¢?