Circumference of a Circle Relationships and How to

Circumference of a Circle Relationships and How to Calculate

The C÷d= Relationship Complete the following activity: • on a blank sheet of paper, draw a circle with any diameter of your choice • explain how you can use the C ÷ d = Π relationship to find the circumference of your circle (do not measure the circumference) • use this method to calculate the circumference then use a strategy to measure the circumference • compare your answers - what do you notice?

Calculating Circumference 1) When d is known: A pizza has a thin string of cheese baked inside the crust. The string of cheese goes around the circumference of the pizza. What length of cheese is stuffed into the crust of the pizza? Round your answer to the nearest cm.

Solution • use the formula for Circumference of a circle: C = Π x d • the diameter in this problem is 30 cm

Calculating Circumference 2) When r is known: Alysia is designing a mousetrap-racer for her science class. Determine the circumference of each wheel. Round your answer to the nearest cm.

Solution • Use the formula: C=2 xΠxr (also written as C = 2Πr) • the radius of each wheel is 6 cm

Extension How far will the mousetrap racer go if the wheels spin eight full rotations? Round your answer to the nearest tenth of a metre (watch your units).

Remember: • always include proper units in your final answer to any measurement problem . • the equal sign with a dot on top (=) means "is approximately equal to" and is used when rounding your final answers

Key Ideas • turn to pg 19 in your textbook and record the Key Ideas at the top of the page • don't forget to include the diagrams

Practice • Complete the following questions in your notebook – Textbook pg. 19 -21 #11, 13, 14, 15 Challenge: 17 – if you do not quite get how to calculate circumference complete #4, 8, and 10 before attempting the questions above