# 2.NBT.A.1 Flawed Reasoning Place Value

## 2.NBT A.1 Flawed Reasoning Place Value

Evidence Statement 3.C.4-7 Disti nguish correct explanation/reasoning from that which is flawed, and if there is a flaw in the argument, present corrected reasoning. (For example, some flawed student reasoning is presented and the task is to correct and improve it.)  Content scope: Knowledge and skills articulated in 2.NBT (securely held knowledge from previous grade)

### Ribbon Count

The table below shows the number of ribbons a swim team earned during their swim season.

Ribbon Count

## Part A

Jasleen says the team won 619 because 3+2+1=6, and 4+6+9=19.

Jasleen is incorrect in her reasoning.

• Explain why Jasleen is incorrect in her thinking.
• Write an equation or equations to find  the correct total number of ribbons earned.

Enter your explanation and equation or equations in the space provided.

## Part B

Jasleen says the team won 25 less third place ribbons then first place ribbons because 3-1=2

and 9-4=5.

Jasleen is incorrect in her reasoning.

Explain why Jasleen is incorrect in her thinking.

•  Write an equation or equations to find how many less third place ribbons were earned than first place.

Enter your explanation and equation or equations in the space provided.

## Scoring Rubric Part A

Score 2 Student response includes the following 2 elements.

Reasoning component = 1 point

The student explains that Jasleen did not use place value correctly.

Computation component = 1 point

The student provides a correct equation or equations to show how the correct number of ribbons earned. ( 34 + 26 + 19= 79 )

Notes:  If a computation mistake is made, credit cannot be given for the computation component, but 1 point can be given for a valid explanation.

Score 1 Student response include 1 of the above elements.

Score 0 Student response is incorrect or irrelevant.

## Scoring Rubric Part B

Score 2 Student response includes the following 2 elements.

Reasoning component = 1 point

The student explains that Jasleen did not use place value correctly.

Computation component = 1 point

The student  provides a correct equation or equations to show how many less third place ribbons were earned. ( 34-19=15 or other valide equation)

Notes:  If a computation mistake is made, credit cannot be given for the computation component, but 1 point can be given for a valid explanation.

Score 1 Student response include 1 of the above elements.

Score 0 Student response is incorrect or irrelevant.