The Great Pacific Garbage Patch activity involves an urgent environmental issue that students can discuss. It engages students in the interpretation of visual data, measurements, units, and the area of regular and irregular figures.

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### Jon R. Star, Soobin Jeon, Rebecca Comeford, Patricia Clark, Bethany Rittle-Johnson, and Kelley Durkin

CDMS is a routine that allows teachers to organize instruction around students’ mathematical discussions and multiple problem-solving methods.

### Rick Anderson and Peter Wiles

Recognizing the complex nature of students’ geometric reasoning, we present guidelines and suggestions for implementing a Guess My Shape minilesson that focuses students’ attention on properties and attributes of geometric shapes.

### Gina Kling and Jennifer M. Bay-Williams

Basic fact fluency has always been of interest to elementary school teachers and is particularly relevant because a wide variety of supplementary materials of varying quality exist for this topic. This article unpacks eight common unproductive practices with basic facts instruction and assessment.

### Rebecca Robichaux-Davis, Cheng-Yao Lin, Jennifer M. Bay-Williams, and Aviva Hamavid

Growing Problem Solvers provides four original, related, classroom-ready mathematical tasks, one for each grade band. Together, these tasks illustrate the trajectory of learners’ growth as problem solvers across their years of school mathematics.

### Jeff Gregg, Diana Underwood Gregg, and Introduction by: Melissa Boston

From the Archives highlights articles from NCTM’s legacy journals, as chosen by leaders in mathematics education.

### Derek A. Williams, Kelly Fulton, Travis Silver, and Alec Nehring

A two-day lesson on taxicab geometry introduces high school students to a unit on proof.

### S. Leigh Nataro

Ear to the Ground features voices from several corners of the mathematics education world.

### Michael S. Meagher, Michael Todd Edwards, and S. Asli Özgün-Koca

Using technology to explore a rich task, students must reconcile discrepancies between graphical and analytic solutions. Technological reasons for the discrepancies are discussed.