2. 3:2 powerpointmaths.com Quality resources for the mathematics classroom Reduce your workload and cut down planning Enjoy a new teaching experience Watch your students interest and enjoyment grow Key concepts focused on and driven home Over 100 files available with many more to come 1000’s of slides with nice graphics and effects. powerpointmaths.com Get ready to fly! © Powerpointmaths.com All rights reserved.

3. The Circumference of a Circle 1 2 3 diameter(d) Circumference (C) How many times does the diameter fit around the circumference? Choose your number. 11½22½33½4  = d radius In terms of the radius: C =? C =2  r

4. It’s the same for all circles! The Circumference of a Circle

5. Find the circumference of the following circles. C =  d C = 2  r 8 cm 1 9.5 cm 2 C =  d C=  x 8 C = 25.1 cm (1 dp) C =  d C=  x 9.5 C = 29.8 cm (1 dp)

6. C = 2  r C = 2 x  x 3 C = 18.8 mm (1 dp) C = 2  r C = 2 x  x 2.1 C = 13.2 m (1 dp) The Circumference of a Circle Find the circumference of the following circles. C =  d C = 2  r 3 mm 4 2.1 m 3

7. 23 cm 7.5 cm Find the circumference of the tyre and steering wheel. C =  d C=  x 23 C = 72.3 cm (1 dp) C = 2  r C = 2 x  x 7.5 C = 47.1 cm (1 dp)

8. The Circumference of a Circle Find the perimeter of the following semi-circles. C =  d C = 2  r 8 cm 1 9.5 cm 2 Perimeter = ½  d + d = ½ x  x 8 + 8 = 20.6 cm (1 dp) Perimeter = ½  d + d = ½ x  x 9.5 + 9.5 = 24.4 cm (1 dp)

9. Perimeter = ¼ ( 2  r) + 2r = ¼ x 2 x  x 6 + 2 x 6 = 21.4 cm (1 dp) Perimeter = ¾(2  r) + 2r = ¾ x 2 x  x 8.5 + 2 x 8.5 = 57.1 cm (1 dp) The Circumference of a Circle Find the perimeter of the ¼ and ¾ circles. C =  d C = 2  r 3 4 6 cm 8.5 cm

10. The Circumference of a Circle Find the diameter/radius of the following circles. C =  d C = 2  r C = 25 cm find the diameter. 5 6  d = 25 d = 25/  d = 8.0 cm (1 dp) 2  r = 30 r = 30/(2  ) r = 4.8 cm (1 dp) C = 30 cm find the radius.