# The Circle 1. Know the names of a circles features 2. Calculate the circumference Why am I doing this? A wheel is a circle! Circles in design – Mickey.

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The Circle 1. Know the names of a circles features 2. Calculate the circumference Why am I doing this? A wheel is a circle! Circles in design – Mickey Mouse is made from circles A real favourite SAT and GCSE question OK - What have I got to do?

Name these Features The distance from the centre to the edge The distance from one side to the other passing through the centre The distance all of the way round the edge The blue line

The distance from the centre to the edge RADIUS The distance from one side to the other passing through the centre DIAMETER The distance all of the way round the edge CIRCUMFERENCE The blue line CHORD Sector Segment

APPROXIMATELY FINDING THE CIRCUMFERENCE Level 5

APPROXIMATELY what is the relationship (connection) between a circles diameter and its circumference?

To APPROXIMATELY find the CIRCUMFERENCE MULTIPLY the DIAMETER by 3 (C = 3 x d) RadiusDiameterCircumference 4 8 12 10 5 15 18 30 42

To APPROXIMATELY find the CIRCUMFERENCE MULTIPLY the DIAMETER by 3 (C = 3 x d) RadiusDiameterCircumference 2412 4824 61236 102060 51030 153090 3618 51030 71442

OAA A circle has a diameter of 10 cm. APPROXIMATELY (ROUGHLY), what is its circumference? A circle has a circumference of 18 cm. Approximately, what is its diameter? 30 cm 6 cm

Calculate the Circumference Using the Correct Formula Level 6

Diameter = 12 cm C = d C = 3 X 12 C = 36 How to calculate the circumference The symbol is the Greek letter pi. It stands for a number that can never be found exactly. It is approximately 3.14 Evaluate the CIRCUMFERENCE Always, write the formula (rule )

Diameter = ?cm C = d d = C ÷ d = C ÷ 3 d = 40 ÷ 3 d = 13.333333 How to calculate the diameter from the circumference If the circumference is 40 cm. evaluate the DIAMETER Always, write the formula (rule )

DiameterRadiusCircumference 124 214 317 430 522 6120 778 888 9120 10340 Remember d = 2 X r r = d ÷ 2

DiameterRadiusCircumference 1241275.36 214743.96 33417106.76 46030188.4 5221169.08 612060376.8 715678489.84 817688552.64 938.2219.11120 10108.2854.14340

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