A grocery store bought ice cream for $2.90 per half gallon and stored it in two freezers. During the night, one freezer malfunctioned and ruined 13 half gallons. If the remaining ice cream is sold for $3.96 per half gallon, how many half gallons did the store buy if they made a profit of $52.40?

Solution : -

cost of 13 half gallons = 13 * $2.90 = $37.7

Now let the gallons of other freezer = x, then

$3.96x = $37.7 + $52.40

3.96x = $90.1

x = $90.1 / 3.96

x = 22.8

Or by rounding off

x = 23

Now the total number of gallons did the store buys = 23 + 13 = 36 half gallons