Lesson 10

Finding the Radius From a Given Circumference or Area

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SWBAT find the radius or diameter of a circle given its circumference or area

Big Idea

It’s a simple lesson that allows students to focus their attention on an important skill.

Teacher Model

5 minutes

Guided Practice

10 minutes

I would like students to solve these problems using the teacher model.  However, GP5 provides a chance for us to discuss the structure of the measurements (MP7).  As students explain their thinking here they have a chance to attend to precision (MP6) as they are careful to distinguish between the value being a square of the radius or representing the diameter.

Independent Practice

15 minutes

I will ask students to represent the problems in an equation, even if they see the shortcut, however, they do not have to follow the steps.  A brief explanation of how they know the radius and diameter is sufficient (MP3).  Students then have 4 extension problems where 3.14 was used for PI.  Now it is not as easy to “eyeball” the radius or diameter so it is a bit more helpful to model the problem using the formula (MP4).

Exit Ticket

5 minutes

The exit ticket is in multiple choice format.  I have chosen distracter answer choices that reflect common errors when working with radius, diameter, and square roots.