Subtract within 1000 using various representations, strategies, and algorithms. Warm up with a Mystery Math Mistake to find a mistake made in using an algorithm for addition and subtraction. Subtract ...

NARRATION: Back in the deepest, darkest depths of time, there lived a great mathemagician called Hypatia. Numbers fell under her spell one by one. With them, Hypatia could do anything. Now, Hypatia is ...

Students put all of their addition and subtraction skills together to solve equations. In this lesson, students put all of their addition and subtraction skills together to solve equations. Julia ...

Here is a part-whole model. Sometimes the model is rotated. It looks different, but it still has two parts and a whole. We can use this model to help us solve problems. We can put 4 things in one of ...