Solve word problems using a checklist. Engage in a Number Talk to find "how many." Solve addition and subtraction word problems with a Step-by-Step Visual Model checklist. Understand what the problem ...

Solving arithmetic problems, even simple subtractions, involves mental representations whose influence remains to be clarified. Visualizing these representations would enable us to better understand ...

The original version of this story appeared in Quanta Magazine. The simplest ideas in mathematics can also be the most perplexing. Take addition. It’s a straightforward operation: One of the first ...