If you fell for this, boy do we have some more brainteasers for you. If you came up with 5,000, then congratulations: You're not alone. But you're also not correct. The actual right answer is 4,100.

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 ...

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 ...