fozzzy wrote:

John bought a total of 12 Mangoes and Oranges. Each Mango costs 80 cents and each orange costs 60 cents. If the average price of the 12 mangoes and oranges that John originally purchased was 65 cents, then how many oranges needs to return to raise the average price of his purchase to 72 cents?

a) 4

b) 5

c) 6

d) 7

e) 8

We can let the number of mangos = m and number of oranges = r. We can create two equations:

m + r = 12

m = 12 - r

and

65 = (80m + 60r)/12

780 = 80m + 60r

78 = 8m + 6r

39 = 4m + 3r

Since m = (12 - r), we have:

39 = 4(12 - r) + 3r

39 = 48 - 4r + 3r

9 = r

Since r = 9, m = 3.

Let’s let x = the number of oranges to return. We can create the following average equation:

72 = [80*3 + 60*(9-x)]/(12 - x)

72(12 - x) = 240 + 540 - 60x

864 - 72x = 780 - 60x

84 = 12x

7 = x

Answer: D

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