What is the amount of orange juice as a mixed number gallons if Bob counted 27 half-gallons in his store?

Since 1 gallon is equivalent to 2 half-gallons, we can calculate the amount of orange juice as follows:

Number of gallons = (Number of half-gallons) / 2

Number of gallons = 27 / 2

Number of gallons = 13.5

Therefore, the amount of orange juice is 13 and 1/2 gallons.