A customer walks in to a lighting store with a broken ceiling light, and the solution to finding a replacement glass illuminates an alternative approach to finding the circumference and area of a circle without knowing the circle’s center, radius, or diameter.

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## Broken Ceiling Lights: Circular Area Without the Radius

### Nicholas J. Gilbertson

## GPS: Teaching Shapes Inclusively

### Samuel Otten, Tiffany J. LaCroix, Faustina Baah, and Rebekah Hanak

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.

## GPS: Triangle Explorations and Constructions Using Robots

### Hyejin Park, Tuğba Boz, Amanda Sawyer, and James C. Willingham

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.

## Teaching Angle as Turn Using a Code.org Lesson

### Stacy K. Boote and Terrie M. Galanti

Elementary school students use physical manipulatives (e.g., pattern blocks) to make sense of the geometry and measurement ideas in a Code.org block-based programming lesson.

## Exploring Sequences Related to Medial Triangles

### José N. Contreras

## Developing Property-Based Geometric Reasoning

### 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.

## Puddle Play!

### Deanna Pecaski McLennan

## Children’s Games and Games for Children

### Nat Banting and Chad Williams

This article examines the mathematical activity of five-year-old Liam to explore the difference between the mathematics games designed for children and the children's games that emerge through playful activity. We propose that this distinction is a salient one for teachers observing mathematical play for evidence of mathematical sense making.

## Triangles from Three Points

### Wayne Nirode

Using technology to solve triangle construction problems, students apply their knowledge of points of concurrency, coordinate geometry, and transformational geometry.

## Mathematical Explorations: Find the Distance: No Formula Necessary

### classroom-ready activities

### Ryota Matsuura and Yu Yan Xu

This activity involves finding the distance between two points in a coordinate plane and emphasizes reasoning from repeated calculations, which is one of the mathematical practices specified by the Common Core State Standards for Mathematics.