Working: Find common factors of 72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72
Work out which ones multiply together to make 72 and as the question states that the length is twice the width, we need to find two numbers that multiply to make 72 and one of the numbers is double the other number.
Given that the dealer sells a dozen tires for $240, every 3-tire set costs $60. There are six 2-tire sets in a dozen. Thus, his total revenue should be $360. The total profit is the difference between the total revenue and the total cost. The answer is therefore, the first choice, $120.