Question

a store bought milk for $2.50 per half gallon and stored it in two refrigerators. During the night one refrigerator malfunctioned and ruined 13 half gallons. If the remaining milk is sold for $3.94 per half gallon, how many half gallons did the store buy if they made a profit of $89.90?

Answer 1

Find profit per half gallon
$3.94-$2.50 = $1.44

Find out how much money was lost because of fridge
13 * $2.50 = $32.50

Find out how much money the store needs to make to make $89.90 profit
$32.50 + $89.90 = $122.4

Find how many half gallons bought
$122.4/$1.44 = 85

85 Half gallons were bought by the store.

Answer 2

let the number of half gallons bought = x
cost price of x half gallons = 2.50x

spoiled = 13 half gallons
left = (x -13) half gallons
selling price of (x - 13) gallons = (x-13)*3.94 = 3.94x - 51.22

profit = selling price - cost price = (3.94x - 51.22) - (2.50x)
= 3.94x - 2.50x -51.22
= 1.44x - 51.22
ATQ, profit = 89.90

so 1.44x - 51.22 = 89.90
1.44x = 89.90 + 51.22
x = 141.12/1.44
x = 98
so 98 half-gallons were bought by the store

Answer 3

checking the answer
cost price of 98 half-gallons = 98*2.50 = 245
half-gallons sold = 98 -13 = 85
selling price of 85 half-gallons = 85*3.94 = 334.90

profit = selling price - cost price = 334.90 - 245 = 89.90