## Archive for September, 2013

### Subtraction Algorithm

Once students have spent time understanding the concept of subtraction and modelling how to regroup, they are ready for the algorithm. At some point, they simply have to memorize the algorithm. That is where this chant comes in:

This is how the chant changes when there are zeros:

### Geometric Thinking

We are starting to do a weekly hour of math exploration every Friday. For the next five Fridays that time will focus on Geometric Thinking. Students will be working on the following standard:

CCSS.Math.Content.3.G.A.1 Understand that shapes in different categories (e.g., rhombuses, rectangles, and others) may share attributes (e.g., having four sides), and that the shared attributes can define a larger category (e.g., quadrilaterals). Recognize rhombuses, rectangles, and squares as examples of quadrilaterals, and draw examples of quadrilaterals that do not belong to any of these subcategories.

This standard requires students to spend a lot of time identifying properties and then sorting and classifying shapes based on their properties. They will need to learn a lot of new vocabulary. I have found it is best for students to split this up into one category of shape per week. In our case, every Friday students will learn to look for a new property. They will also learn the new verse to a song that will help them memorize the names of the shapes.

*These are the lyrics to the song (to the tune of The Twelve Days of Christmas):*

*On the first day of Geometry, my teacher gave to me: a quadrilateral with four sides!*

*On the second day of Geometry, my teacher gave to me: parallelogram and a quadrilateral with four sides!*

*On the third day of Geometry, my teacher gave to me: rectangles with right angles, parallelogram and a quadrilateral with four sides!*

*On the fourth day of Geometry, my teacher gave to me: equal-sided rhombus, rectangles with right angles, parallelogram and a quadrilateral with four sides!*

*On the fifth day of Geometry, my teacher gave to me: square’s the VIP, equal-sided rhombus, rectangles with right angles, parallelogram and a quadrilateral with four sides!On the fifth day of Geometry, my teacher gave to me: square’s the VIP, equal-sided rhombus, rectangles with right angles, parallelogram and a quadrilateral with four sides!*

The video above is of some of my former fifth graders (now seventh graders) singing the song. They make a small mistake during the fourth verse because they learned the song two years ago, but you get the idea.