Categories
Ratios & Proportional Relationships Ratios and Proportions

Proportions

What’s the mistake? Why this mistake in particular?

Thanks again to Louise Wilson for the submission.

Categories
Reasoning with Equations and Inequalities Solving Linear Equations

Solving Equations

The student clearly needs more practice with solving equations. Fine. But why did the student make this mistake, in particular? After all, there are dozens of ways to mess up this problem. Why was this way tempting?

Today’s submissions comes Louise Wilson, who blogs over at Crazed Mummy.

Categories
Graphing High School: Modeling linear functions Linear, Quadratic, and Exponential Models*

Linear Modeling and Graphing

What’s the mistake? How would you help?

Thanks to John Weisenfeld for the submission.

Categories
Algebra 1 linear functions Linear, Quadratic, and Exponential Models* slope

Slippery Slope

The submitter of this mistake reports that the student is a “high flyer.”

  1. What is this student’s confusion?
  2. Why made this mistake so tempting? After all, if a student just doesn’t understand “slope” there are a million things that they could do wrong. Why this one?

Thanks to Jeff de Varona for the submission. Go check out his blog and follow him on twitter.

Categories
exponents The Number System

Zero and Exponents

This post is brought to you by David Wees. Thanks, David!

Categories
Distributive Property exponents Expressions and Equations

The Distributive Property of Exponents

Why is this mistake so enticing, and how might you help students avoid it?

[Compare: http://mathmistakes.org/?p=396]

Thanks again to Anna Blinstein for the submission. Follow her! Virtually! Not literally!

Categories
Arithmetic with Polynomials and Rational Expressions exponents Rational Expressions Seeing Structure in Expressions

Cross-Multiplying

What’s the mistake? Diagnose the disease, and find the cure in the comments.

Thanks to Anna Blintsein for the submissions. Go follow her on twitter!

Categories
Arithmetic The Number System

Sad faces and Negative Numbers

There’s some context that’s necessary for this post. So go read Nathan Kraft’s post about arithmetic with negative numbers.

What’s the mistake? Thoughts?

This piece of student work is kindly submitted by 3-act maven Chris Robinson.

Categories
Algebra 1 Grade 4 Numbers & Operations -- Fractions

Equivalent Fractions

Same question, but 6 different pieces of student work.

What is a lesson that you can glean from this question and these student responses? Say you’re the teacher of this class. What do you do next? (For full context: the submitted pictures are from a 9th grade Algebra 1 classroom.)

Categories
Building Functions exponents High School: Functions

Matching a recursive function to a table

What does the student know? What’s the mistake? How would you help?