So if the length around the jar is 18 inches and we know that there is 12 inches in a foot, and 3 feet in a yard and $ 4.80 per every 3 feet. These become basis numbers. 18in- 12inch= 6 inch. So now we have 1 1/2 feet of ribbon to cover the circumference of the jar. Now we are left to answer the second question how much does it cost per foot? We can divide 4.80 by 3 to see the total cost of a foot of ribbon. That turns to 1.60 per foot. We divide that by two to cover the 6 inches. And the answer is $2.40 for 1 1/2 feet of ribbon