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Invented by Leonardo Torres in 1920, the Torres calculating machine is a machine that solves essential addition, subtraction, multiplication, and division problems using a simple manner. It was a ...

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 ...

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 ...

Match fun story problems with the correct addition or subtraction expression. Join Mrs. Gray for number talk with the Counting Buddy Junior. Then get ready to match fun story problems with the correct ...

Our pitch calls have yielded remarkable stories, and we want to keep that ball rolling. So it’s time for the next theme. As a refresher: These should be adventures with technology—stories that ...

Here you will find a video about addition and subtraction. Watch this, and then test your knowledge with a short quiz before exploring the rest of the collection. This section contains videos from our ...