Getting Started 
Misconception/Error The student does not understand unit price and does not take unit price into account in making a decision. 
Examples of Student Work at this Level The student:
 Chooses the cereal with the lowest price or the greatest quantity without calculating a unit price.
 Multiples the prices by the quantities and may or may not use these products to make a decision.
 Attempts to find a common multiple of the given quantities in order to make a comparison.

Questions Eliciting Thinking Do you know what unit price means? Do you know how to calculate a unit price?
Suppose 2 ounces of cereal cost $1.00. How much would each ounce cost? If 4 ounces of another cereal cost $1.20, how much would each ounce cost? Does this help you make a decision about which is the best buy?
What would the product of 16 ounces and $3.50 mean in the context of this problem? 
Instructional Implications Review the concepts of rates and ratios. Describe rates and ratios as comparisons of two quantities and point out that the quantities might not contain the same units of measure. Guide the student to use ratio language (e.g., “for each,” “for every,” and “per”) when interpreting rates or describing their meaning. Use tape diagrams and double number lines to model rates.
Introduce the student to the concept of a unit rate and guide the student to calculate unit rates from given rates. Assist the student in using unit rates to make comparisons and draw conclusions in contextual problems. 
Moving Forward 
Misconception/Error The student understands to calculate the unit price (or unit weight) but is unable to complete the calculations or does not know how to interpret them to make a decision. 
Examples of Student Work at this Level The student:
 Attempts to calculate unit price or unit weight for some of the cereals but is unable to complete the calculations.
 Calculates the unit prices or weights (possibly with errors) but draws conclusions that are not consistent with the calculations.

Questions Eliciting Thinking It looks like you were trying to calculate the unit price of this cereal but stopped. Could you complete this calculation?
Why did you divide the cost (or the weight) by the number of ounces (or the cost)? What did that tell you?
How did you decide which cereal is the best buy? 
Instructional Implications Assist the student in completing any unfinished calculations. Consider providing the student with a calculator to complete calculations and then reassess whether the student understands the meaning of unit rates and how to use them to make decisions about the best buy.
Guide the student to interpret the meaning of his or her calculations in the context of the problem. Review the meaning of “best buy” and ask the student to use his or her calculations to determine which cereal is the best buy. Provide feedback as needed.
Provide additional opportunities to calculate and use unit rates to make comparisons and draw conclusions in contextual problems.
Consider implementing MFAS task 6RP.1.2 Writing Unit Rates. 
Almost There 
Misconception/Error The student makes a computational error when calculating a unit rate. 
Examples of Student Work at this Level The student makes a computational error which may or may not lead to an incorrect conclusion.

Questions Eliciting Thinking I think you may have made a mistake here. Can you check your work to see if it is correct?
Will correcting this mistake change your conclusion? Why? 
Instructional Implications Assist the student in locating and correcting any computational errors. Ask the student to determine if correcting the error(s) alters the conclusion.
Provide additional problems in which unit rates must be calculated and interpreted. Pair the student with another Almost There student in order to compare answers and reconcile any differences. 
Got It 
Misconception/Error The student provides complete and correct responses to all components of the task. 
Examples of Student Work at this Level The student correctly computes each unit price and determines that Chocolate O’s offers the most cereal for the least amount of money since it has the lowest price per ounce (or the greatest weight per dollar).

Questions Eliciting Thinking Are there any cereals that you can eliminate without doing any calculations?
Suppose a student divided 16 ounces by $3.50 getting a value of about 4.57. What would this value mean in the context of this problem? 
Instructional Implications Ask the student to use a unit rate to determine how much another quantity, such as 24 ounces, of one of the cereals would cost. Encourage the student to write a proportion and model the use of proportion language to read the equation (i.e., 1 ounce is to 22 cents as 20 ounces is to c cents). Allow the student to use strategies based on an understanding of equivalent ratios to find the missing value rather than techniques such as cross multiplying. 