## Recognize Angles as Geometric Shapes

#### Aligned To Common Core Standard:

**Grade 4 Geometry** - 4.MD.5

How to Guess on the Measurement of an Angle The easiest way to guess the angle you want to measure is through the use of a protractor. However, not always, you will have a protractor at your disposal, and that can be a measure issue for some students. Estimating measurement of an angle is much easier than what most students think. You can estimate the angle of measurement using basic geometric principles that are used in triangles. For example, one of the basic principles of estimating a missing angle in a triangle is using the formula: All angles of the triangle sum up to 180 degrees a1 + a2 + a3 = 180 Using this formula, we can easily dictate the missing angle by putting in the other two values. For example: Angle 1 = 56 degrees Angle 2 = 77 degrees Angle 3 =? Formula: a1 + a2 + a3 = 180 56 + 77 + a3 = 180 a3 = 180 – 133 a3 = 47 Another basic geometric formula can be used for determining the missing angle in a circle. It is a basic mathematical principle that a circle is equal to 360 degrees. Hence, if a circle or a pie is divided into three equal pieces, and you only know the value of two angles, the remaining angle can easily be calculated. Students can use these worksheets to better understand angles and their role in geometry.

### Printable Worksheets And Lessons

- Measuring Angles Step-by-Step
Lesson- We meet up with right angles to get this party started.

- Guided Lesson -
A nice guesstimate the angle activity.

- Guided Lesson Explanation
- I like to explain these by making the angles relative to right
angles and straight lines.

- Practice Worksheet -
I really like to give kids this right after they start using a protractor.
The standards list it first though.

- Matching Worksheet - Find the two matching angles. Beware they are all flipped around.

#### Homework Sheets

We give some angles and ask you to estimate their measures. This is a great skill to have mastered.

- Homework 1 - What is the measure of this angle? Choose the best estimate.
- Homework 2 - This angle is about 1/9 the size of a right angle
- Homework 3 - Use observational fractions to estimate bigger angles.

#### Practice Worksheets

More practice on guessing the measure of angles out of thin air.

- Practice 1 - What is the approximate measure of this angle?
- Practice 2 - You can also classify the angles for bonus points.
- Practice 3 - Have another round of this for good luck.