Scientists often use rates to express quantities and to make changes from one unit to another. The ability to find the unit price for a particular object you wish to purchase is often a valuable tool for comparing prices.
Unit price is the cost of one of a particular item.
You can compare unit prices to help determine which item is a better buy. In this case, the 36-ounce box is a better buy. It is important that students learn to estimate the answers to rate and ratio problems. Having students estimate answers indicates the depth of their understanding and it gives them a way of checking to see if their answers are reasonable. One way to estimate an answer is to estimate a unit price and then multiply the estimate by the number of units needed.