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Category Archives: Geometry

A Parallelogram is a Rhombus

Posted on May 5, 2013 by mpershan | 3 Replies

ASN 6 2 ASN 6

These are some “Always, Sometimes, Never” questions. Like, “Is it always, sometimes or never true that a rhombus is a parallelogram.”

What’s the fastest way to help these students?

(Thanks for the submission, Tina C!)

Posted in Geometry, Quadrilaterals.

Sqrt(1) and Right Triangles

Posted on March 19, 2013 by mpershan | 4 Replies

IMG_2614

This mistake seems ripe for theorizing. Would a kid make this mistake if the hypotenuse was 4 instead of 10?

Posted in Geometry, Geometry, Pythagorean Theorem, Right Triangles.

Area of Walls

Posted on October 31, 2012 by mpershan | 7 Replies

What’s the mistake? How can you help the kid?

When you’re done with this post, go check out Mary Dooms’ blog and go follow her on twitter. Thanks for the submission, Mary!

Posted in Area, Geometry, Middle School, Perimeter and Volume.

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This site is about compiling, analyzing and discussing the mathematical errors that students make. Every day a new mistake is posted. The site is edited by Michael Pershan, a high school math teacher from NYC.

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To keep the site going we need lots of interesting mistakes. To submit a picture of mathematical work, email mathmistakes@gmail.com

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