Count back & use the relationship between addition and subtraction to subtract within 20. Warm up with a Mystery Math Mistake to find the error in DC's addition. Use ...

Add and subtract within 100 using compose, decompose, and place value strategies. Engage with a number talk to sum near-doubles using compensation. Add and subtract within 100 in more than one way.

The calculator on your Apple devices can do more than add, subtract, multiply and divide. Here's how it can help you with all kinds of math problems.

When you are doing arithmetic by hand because your calculator’s batteries just gave up and your laptop is in the other room, it’s best if you can check your calculations with a different process than ...