Circles Circles Feedback Pythagorean Theorem

Circumference and Right Triangles

circle mistake

Say something smart in the comments about why kids forget “little” things on problems.  Or, alternatively, disagree with the premise of my first question. (How’s that for a lousy prompt?)

Thanks to Mark Kingsbury for the submission!

Geometric Measurement and Dimension Geometry High School: Geometry Pythagorean Theorem Quadrilaterals Similarity, Right Triangles and Trigonometry

Baseball Fields and Geometry

What made this question hard for the student? How come they got it wrong? Why did the student get it wrong in this particular way?

Today’s submission comes from Tina Cardone, who blogs at Drawing On Math.

Geometric Measurement and Dimension Geometry


Define “Hexagon”:

What does this student know about hexagons? What does the student think he knows, but doesn’t? What does the mistake reveal about his thinking, and what would you do to help?

G-GPE.2 Quadratic Functions Quadratic Functions

Equation of Parabola

From the student’s work, what can we infer that the student knows?  What is the student thinking? How would you help?

G.CO.10 Isosceles Triangles Proofs

Problems with Proofs

The proof above isn’t great. In the comments, take on any of the following questions (or any others):

  1. Sometimes kids slap stuff together when they’re confused, and other times they’re substantively mistaken. Which is this, and what evidence supports your position?
  2. How would you help this student recognize that the logic in his proof doesn’t flow?
  3. What would your next steps be in working with this student? What sorts of problems would you ask him/her to solve?
  4. From the picture above, what evidence of knowledge do we have?


Algebra 2 G-SRT.10 Law of Cosines Law of Sines Trigonometry

Trigonometry – Find the missing angle


My sense is that this mistake isn’t as interesting as the rest, but it’s a pretty common one that I see in Trigonometry. The question is, what sort of activity would help this student out?