Problems to Ponder provides 28 varying, classroom-ready mathematics problems that collectively span PK–12, arranged in the order of the grade level. Answers to the problems are available online. Individuals are encouraged to submit a problem or a collection of problems directly to mtlt@nctm.org. If published, the authors of problems will be acknowledged.

# Browse

### Marina Basu, Karen Koellner, Jennifer K. Jacobs, and Nanette Seago

This set of tasks progressively engages students in geometric proportional reasoning.

### A. Susan Gay, Jeanine Haistings, and Jason L. Rucker

The authors describe a fourth-grade lesson that promotes understanding of angle as a dynamic figure through use of a real-world tool used by physical therapists to measure joint motion.

### Nasim Chenari

This article describes how fortuitous mathematical moments should be noticed, encouraged, embraced, and capitalized upon.

### Amanda L. Cullen

Any ability grouping in mathematics education is an inequitable structure that perpetuates privilege for a few and marginality for others. Ability grouping practices often occur with good intentions; we want to understand children’s learning needs and then tailor the content,

### Joshua David Jones

To be literate in a society where the information shared online is often exploited, learners should be exposed to multiple aspects of contemporary predictive modeling. Explore a lesson in which students learned an algorithm used in practice to automate the process of making recommendations.

### Eric Cordero-Siy and Hala Ghousseini

Three deliberate teaching practices can help students strengthen multiple connections to a unifying concept.

### Surani Joshua, James Drimalla, Dru Horne, Heather Lavender, Alexandra Yon, Cameron Byerley, Hyunkyoung Yoon, and Kevin Moore

The Relative Risk Tool web app allows students to compare risks relating to COVID-19 with other more familiar risks, to make multiplicative comparisons, and to interpret them.

### F. Paul Wonsavage

Three approaches to the Doughnut task highlight how representing functions in multiple ways can support student understanding in interpreting key features of functions within a context.

### Elizabeth G. Arnold, Elizabeth A. Burroughs, Mary Alice Carlson, Elizabeth W. Fulton, and Megan H. Wickstrom

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