3.OA.D.8  Solving 2-Step Word Problems (Flawed Reasoning)

 Evidence Statement 3.C.4-3- Distinguish correct explanation/reasoning from that which is flawed, and-if there is a flaw in the argument-present correct reasoning. (For example, some flawed student reasoning is present and the task is to correct and improve it.) 

School Bake Sale

Rashad is baking cupcakes for a school bake sale. He makes 24 cupcakes on Friday. 

He makes the same number of cupcakes on Saturday. Rashad plans to display his cupcakes on a stand. 

Each stand holds 8 cupcakes.    

 When Rashad gets to the bake sale, there are 3 cupcake stands waiting for him. Alonzo said “You only need three stands because 24 ÷ 8 = 3.” 

Alonzo is incorrect in his reasoning.   

• Explain why Alonzo is incorrect in his reasoning about the number of cupcake stands Rashad needs. 
• Find the number of cupcake stands Rashad needs.
• Explain why your reasoning is correct.

Enter your answer and your explanation in the space provided.

Student Copy

Scoring Rubric

Score of 3 points- Student response includes the following 3 elements. 

•  Reasoning component – 1 point 
• The student explains that Alonzo did not find the total number of cupcakes Rashad made. (The correct number made is 48.)
• Computation component – 1 point 
• The student finds the correct number of cupcake stands Rashad needs. (6)
• Reasoning component – 1 point 
• The student provides an explanation why their answer is correct. 
• Sample Student Response: Alonzo’s reasoning is incorrect because he did not find the total number of cupcakes Rashad made. He needed to add the cupcakes made on Friday to the cupcakes made on Saturday before finding the number of stands needed. 24 + 24 = 48 cupcakes. 48 ÷ 8 = 6. Rashad needs 6 cupcake stands. Rashad needs 6 cupcake stands. 

 Score of 2 points- Student response includes 2 of the above elements. 

 Score of 1 Point- Student response includes 1 of the above elements. 

 Score of 0 Points- Student response is incorrect or irrelevant.