# Constructing Equal-Area Triangles

The origins of this week's Web Sketchpad model date back to the  Connected Geometry curriculum from the mid 1990s. I was one of the co-authors of the curriculum, working at Education Development Center with a  wonderful team of math educators (Al Cuoco, Paul Goldenberg, and June Mark, … Continue Reading ››

# Solving Simultaneous Equations with Common Sense

Simultaneous equations belong in elementary-school mathematics curricula. That's been my mantra for many years, and I want to examine it now in the context of an interactive Web Sketchpad activity. When I say that elementary-age students should encounter simultaneous equations, I don't mean that they should be instructed in the standard algebraic procedure for solving pairs of equations … Continue Reading ››

# Pi Day 2015: Pieces of Pi

For this year’s Pi Day post, I thought I’d continue our Web Sketchpad (WSP) construction theme. But rather than adapting the visualizations from last year’s Pi Day post to the new construction capabilities, I decided to take a different approach. Some time ago, I built a set of custom tools for … Continue Reading ››

# WCYDWT: A Ball, a Trash Can, and Web Sketchpad

Dan Meyer has posted a number of "What Can You Do With This?" activities on his blog. (Activities is probably too prescriptive a word; they're more in the nature of prompts for student thinking, noticing, and wondering.) One of the first was the image below, which he made by superimposing frames from a … Continue Reading ››

# Moving Beyond Formulas When Investigating Triangle Area

For the past year, my blogging partner Scott and I have worked with the team of Everyday Mathematics to build interactive Web Sketchpad models for their forthcoming new edition. It's been fun for both of us to find ways to insert dynamic mathematics into their K–6 curriculum. Last year, I shared anContinue Reading ››

# Innovative Approaches to Computer-Based Assessment, Part Two

In my previous post, I shared Dan Meyer's analysis of what's wrong with computer-based mathematics assessments. Dan focuses his critique on the Khan Academy's eighth-grade online mathematics course, identifying 74% of its assessment questions as focusing on numerical answers or multiple-choice items. This is a far cry from … Continue Reading ››

# Refutation in a Dynamic Geometry Context

Michael de Villiers teaches courses in mathematics and mathematics education at University of KwaZulu-Natal in South Africa. His website features a wealth of Dynamic Geometry-related books, articles, and sketches. He is the author of the Sketchpad activity module Rethinking Proof with The Geometer's Sketchpad. This blog … Continue Reading ››

# Isosceles Triangle Puzzles

As readers of this blog can probably tell, I like puzzles. I especially enjoy taking ordinary mathematical topics that might not seem puzzle worthy and finding ways to inject some challenge, excitement, and mystery into them. This week, I set my sights on isosceles triangles. It's common to encounter isosceles triangles as supporting players in geometric proofs, but … Continue Reading ››

# Dancing Unknowns: You Haven’t Seen Simultaneous Equations Like These!

When it comes to simultaneous equations, I like to push the bounds of conventional pedagogical wisdom. In an earlier post, I offered a puzzle in which elementary-age students solve for four unknowns given eight equations. Now, I'd like to present a puzzle that might sound even more audacious: Solving for ten unknowns. Oh, and … Continue Reading ››