The grade fives have been learning about 2-D geometry for the past few weeks. We have learned about different properties and types of triangles:

We did this and discovered some types of triangles are impossible:

We have learned about angles:

We have been learning that angles are measured in units called degrees. Degrees are wedge shaped units and there are 360 of them in a circle.

I want the students to have a really solid understanding of degrees and angles so we did lots of activities exploring angles before we used a protractor. They had to determine the angle measures in pattern blocks without using a protractor. First we determined that the square angles were all 90 degrees. We know that a straight angle is 180 degrees so therefore a square angle must be 90 degrees.

and since three triangles fit on a straight 180 degrees then one triangle must be 60 degrees!

Now we can figure out all the rest, just by putting them on the 180 degree straight angle and doing some calculations.

Here is a video from Teacher Tube showing some ways to find the measure of angles

Next we learned how to measure angles using a protractor. A common mistake is reading the wrong set of numbers so I ask the students to label the angle as acute or obtuse first. If they say the angle is acute, which means less than 90 degrees, and they measure 120 degrees, then they know they have used the wrong set of measures.

Our next step is constructing triangles given the length of one side and one of the angles.

Students will have a review package for over the weekend.