1. Name ______ Gr.__ Lesson 4.2 – Circumference of a Circle Jan.__ Objective: to investigate the relationship between the circumference and diameter of a circle.

2. Name ______ Gr.__ Lesson 4.2 – Circumference of a Circle Jan.__ EXPLORE: You will need 3 circular objects of different sizes, string, and a ruler. ➤ Each of you chooses one of the objects. Use string to measure the distance around it. Measure the radius and diameter of the object. Record these measures. ➤ Repeat the activity until each of you has measured all 3 objects. Compare your results. If your measures are the same, record them in a table. If your measures for any object are different, measure again to check. When you agree upon the measures, record them in the table. Object Distance Around (cm) Radius (cm) Diameter (cm) can

3. Name ______ Gr.__ Lesson 4.2 – Circumference of a Circle Jan.__ EXPLORE: O bject Distance Around (cm) Radius (cm) Diameter (cm) can For each object, calculate: distance around / diameter. What do you notice? Note: distance around = Circumference, C

4. Name ______ Gr.__ Lesson 4.2 – Circumference of a Circle Jan.__ EXPLORE: O bject Distance Around (cm) Radius (cm) Diameter (cm) can For each object, calculate: distance around / diameter. What do you notice? Note: distance around = Circumference, C For each object… C / d ≈ 3 or more exactly…

5. Name ______ Gr.__ Lesson 4.2 – Circumference of a Circle Jan.__ EXPLORE: O bject Distance Around (cm) Radius (cm) Diameter (cm) can For each object, calculate: distance around / diameter. What do you notice? Note: distance around = Circumference, C For each object… C / d ≈ 3 or more exactly… C / d = 3.1415926… or pi π

6. Name ______ Gr.__ Lesson 4.2 – Circumference of a Circle Jan.__ π is a decimal that never repeats & never terminates. π cannot be written as a fraction. For this reason, we call π an irrational number. We can rewrite the formula C / d = π to C = πd

7. Name ______ Gr.__ Lesson 4.2 – Circumference of a Circle Jan.__ π is a decimal that never repeats & never terminates. π cannot be written as a fraction. For this reason, we call π an irrational number. We can rewrite the formula C / d = π to C = πd to solve for the Circumference OR d = C /π to solve for the diameter. STUDY THESE 2 FORMULAS!!

8. Name ______ Gr.__ Lesson 4.2 – Circumference of a Circle Jan.__ PRACTICE: page 136 #’s 1,2,4