19 is only 1 away from 20, so you prefer to start by multiplying 20 times 5, which equals 100. Then we need to take away a squadron of 5, because there are actually only 19 squadrons, not 20. 100 take ...

You can find the difference between two numbers in more than one way. You can count up from the smaller number to the larger number. Or, you can count back from the larger number to the smaller number ...

Helping students to develop math fluency takes more than just flash cards. It requires teaching them how to think about ...

Believe it or not, highway numbers actually make sense. Here's the logic behind odd and even routes, and why the system isn't ...

This short but rigorous book approaches the main ideas of linear algebra through carefully selected examples and relevant applications. It is intended for students with various interests in ...