Quadrilateral Review

• Measure the length and width of your desktop.• Measure and calculate the distance around the

outside of your desktop.

• What unit did you use to measure your desks? Why?

• What do we call the distance around the outside of an object?

Group Investigation

• Get into groups of 4– Member 1: Task leader-makes sure all students are

participating and lets me know if the group needs help or has questions

– Member 2: Recorder-keeps group copy of measurements and calculations from activity

– Member 3: Measurer-measures items (other members should also check these measurements)

– Member 4: Presenter-presents the group’s findings and ideas to the class

– Pick your roles now…

. Minds On: Measure the distance around different circular objects.Object Distance Around

(cm)Radius (cm)

Diameter (cm)

StoolBUCKET 54.5cm 9.5cm 19cm

White board maker

5.7cm 0.7cm 1.4cm

Paint 22cm 3cm 7cm

Elephant skin ball

55cm 27.5cm 55cm

Broom handle

7.5cm 1.5cm 3cm

Consolidation:What patterns do you see? What do you notice?

diameter

radius

Perimeter-The distance around a circular object is the circumference

- When you divide c (circumference) by d (diameter), you get a number close to 3.

- When you divide the c (circumference) by the r (radius), you get a number close to 6.

2r = d d = r 3d = c 6 r = c 2

• pi = http://www.piday.org/million/

• is an irrational number

• It never repeats

• It’s value is = 3.14

• is a Greek letter

C = x d or C = d

http://illuminations.nctm.org/Activity.aspx?id=3547

d = 41 cm

Circumference, Diameter, and Pi

C = x (r + r) or C = 2r

r= 30mm

Circumference, Pi, and Radius

Solve:

C = 2 r r= 15cm

Solve:

C = 2 r r= 7cm

Grade 8Learning Goal: I will calculate the circumference of a circle using the formula we generated as a class.

Your job

1. Math Makes SensePage 245-246 # 2, 3, 5, 7*, 8, and 9 OR Reflect

Due: Wednesday November 11, 2015

2. Coming Soon! Quiz on:-the difference between diameter and radius, calculating circumference