Getting Started 
Misconception/Error The student does not demonstrate an understanding of the Pythagorean Theorem or the need to use it to solve this problem. 
Examples of Student Work at this Level The student’s work contains no evidence of the use of the Pythagorean Theorem. The student calculates another quantity such as the area of the TV screen. 
Questions Eliciting Thinking What is this problem asking you to find? Can you draw the diagonal? What type of figure do you see? Are there any right angles? Do you see any right triangles?
Does finding area answer the question about the length of the diagonal?
Do you know what the Pythagorean Theorem says? 
Instructional Implications Provide the student with basic instruction on the Pythagorean Theorem. Be sure to review the parts of a right triangle (e.g., vertices, right angle, acute angles, hypotenuse, and legs). When initially introducing the Pythagorean Theorem, emphasize that it only applies to right triangles. Be very explicit about what the theorem says describing it verbally and with mathematical symbols. Caution the student to be careful not to confuse the legs and hypotenuse when applying the theorem. Give the student the opportunity to find missing lengths in right triangles in both real world and mathematical problems. Include problems in which the length of the hypotenuse is unknown, the length of a leg is unknown, unknown lengths are integers, unknown lengths are rational or irrational numbers, and diagrams must be sketched and labeled. Guide the student to show work completely and in an organized manner.
If needed, review finding and approximating square roots. 
Moving Forward 
Misconception/Error The student makes errors in applying the Pythagorean Theorem. 
Examples of Student Work at this Level The student:
 Does not substitute the correct values for the lengths of the legs or the hypotenuse.
 Finds the square of the hypotenuse but neglects to take its square root.

Questions Eliciting Thinking What is the Pythagorean Theorem? Which variables represent the legs? Which variable represents the hypotenuse? Which sides are the legs of the right triangle in the diagram? Which side is the hypotenuse of the right triangle in the diagram?
Can the diagonal really be 3622 inches? Does that make sense?
What did you actually solve for, c or ? 
Instructional Implications Review the Pythagorean Theorem. Be sure the student is correctly able to identify the right angle, the legs, and the hypotenuse of the right triangle in a diagram. If the student has difficulty distinguishing the legs from the hypotenuse of a right triangle embedded in a diagram, encourage the student to redraw the right triangle separately and label its parts. Give the student the opportunity to find missing lengths in right triangles in both real world and mathematical problems. Include problems in which the length of the hypotenuse is unknown, the length of a leg is unknown, unknown lengths are integers, unknown lengths are rational or irrational numbers, and diagrams must be sketched and labeled. Guide the student to show work completely and in an organized manner.
Remind the student to check for the reasonableness of the answer. 
Almost There 
Misconception/Error The student makes a minor computational error. 
Examples of Student Work at this Level The student:
 Copies a value from the diagram incorrectly. All other work is correct given the error.
 Does not take into account the width of one or both of the TV speakers.

Questions Eliciting Thinking You have a slight error in your work. Can you find it?
What does the 59 inches represent? What is the width of each speaker? What is the width of just the TV screen? 
Instructional Implications Provide feedback to the student regarding any errors made and allow the student to revise his or her work. Encourage the student to carefully label diagrams. Remind the student to show work neatly and completely to avoid careless errors.
Remind the student to check for the reasonableness of the answer within the given context.
Consider implementing the MFAS task Will It Fit? (GSRT.3.8) if not previously used. 
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 determines that the diagonal of the TV is approximately 60 inches.

Questions Eliciting Thinking How did you know to use the Pythagorean Theorem to solve this problem?
Can you restate the Pythagorean Theorem? To what kind of figure does it apply? 
Instructional Implications Challenge the student with more difficult mathematical and real world problems that require the use of the Pythagorean Theorem. For example, ask the student to find the slant height and length of a lateral edge of a square pyramid given its height and the length of a base edge.
Consider implementing the MFAS task Will It Fit? (GSRT.3.8) if not previously used. 