Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. The Circle Circumference of the circle Diameter = Circumference ÷ π Area of a circle Fractions of a circle

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Starter Questions Starter Questions 6cm 3cm

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Learning Intention Success Criteria 1.To revise the basics of the circle. Main Parts of a Circle 1.Remember the terms circumference, diameter and radius. 2.Identify them on a circle. 3.Calculate the circumference using formula. Revision of 2

Level 3 Circumference 14-Aug-15Created by Mr. Lafferty Maths Dept. Main Parts of a Circle Main parts of the circle radius O Diameter Revision of 2

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Main part of a Circle 10cm 2cm Example : Find the length of the circumference (Perimeter) of each circle Revision of 2

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Now try Exercise 1 Ch29 (page 118) Revision of 2 Main part of a Circle

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Starter Questions Starter Questions

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Learning Intention Success Criteria 1. We are learning we can find diameter of a circle if we know the circumference. Finding the Diameter The Circle 2.Solve diameter problems. 1.Understand how to rearrange circumference formula to find diameter.

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. We can easily rearrange the circumference formula so that we have the diameter D on one side. Finding the Diameter The Circle You have 1 minute to rearrange equation. Remember change side change sign

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. C = 62.8 cm Example : Find the diameter of each circle given the circumference. 2 0 c m C =15.7 cm 5 c m Finding the Diameter The Circle

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Now try Exercise 2 Ch29 (page 121) Finding the Diameter The Circle

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Starter Questions Starter Questions 6 5

Level 3 What do we call the distance AB in terms of the large circle. Area of a Circle O A x O A x B What do we call the distance OA in terms of the large circle. circumference Peeling an orange

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. What is the formula for the area of a right-angle triangle. O A x B Use this formula to work out the area for a circle. Area of a Circle

Level 3 Friday, 14 August 2015Friday, 14 August 2015Friday, 14 August 2015Friday, 14 August 2015Created by Mr Lafferty If we break the circle into equal sectors And lay them out side by side We get very close to a rectangle. Area of a Circle Demo

Level 3 Friday, 14 August 2015Friday, 14 August 2015Friday, 14 August 2015Friday, 14 August 2015Created by Mr Lafferty thinner and thinner sectors If we cut the sectors Thinner and thinner then we get closer and closer to a rectangle. Hence we can represent the area of a circle by a rectangle. Area of a Circle

Level 3 Friday, 14 August 2015Friday, 14 August 2015Friday, 14 August 2015Friday, 14 August 2015Created by Mr Lafferty 17 But the area inside this rectangle is also the area of the circle Area of a Circle Area = πr 2

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Area of a circle Q.Find the area of the circle ?Solution 4cm

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Area of a circle Q. The diameter of the circle is 60cm. Find area of the circle?Solution

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. What have we learned so far Area of a Circle

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Now try Exercise 3 Ch29 (page 123) Area of a Circle

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Starter Questions Starter Questions 4

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Learning Intention Success Criteria 1.Recall knowledge of circles so far. 1. We are learning to solve problems by applying our knowledge of circles. Mixed Problems 2.Solve mixed problems by applying all our knowledge so far. The Circle

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Mixed Problems The Circle Things to think about when doing exercise. The area of a semicircle ……. Find whole circle then half it ! The area of a quarter circle …….Find whole circle then quarter it ! Composite area …….Find each area and add them together !

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Mixed Problems The Circle Example 1 : Find the area of the shape 20cm 5 cm Area = rectangle + semicircle

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Mixed Problems The Circle Example 2 : A circle is contained in a square. Find the grey shaded area below. Area = square - circle 8cm

Level 3 14-Aug-15Created by Mr. Lafferty Maths Dept. Now try Exercise 4 Ch29 (page 125) Mixed Problems The Circle