Circles+and+Circumference

= **Chapter 6.6 and 6.7** = = = = **Circles and circumference** =


 * With circles and circumference there are only a few things you need to now, how to work out the diameter from the radius and how to work out the circumference from the radius and the diameter. Here is a diagram labeling the different parts of the circle:**

Here is an explanation of each part of the circle and equation: Circumference: The perimeter of a circle Diameter: The measurement of the widest part of a circle Radius: Half of the diameter Pi: 3.14, the number used in __**every**__ equation

Now I will explain how to turn the radius or diameter, into the circumference: First we will do radius. The equation for this is- C= R x 2 x 3.14. Here is an example, Lets say the radius is 5 cm long, we simply times it by two, making it ten and times that by 3.14, making the circumference, 31.4 cm. Simple, eh?

The Diameter is even easier, the equation for it is- C= D x 3.14. Here is an example, If the diameter is 20 cm long, you would times it by 3.14, making the answer 62.8 cm. This is easy, peasy, japanesey, right? I thought so. Try your luck on these questions:

1: What is the circumference of each of these circles? a.b. c.

2: What is the circumference of each of these circles? a.b.c.

3: Now for multiple choice: a. Ally has worn out her bike wheels and needs to buy new ones. If the radius of the wheels that she currently has is 25 cm, what is the circumference of the wheel/wheel size that she needs to buy? i. 157cm ii. 149cm iii. 162cm b. Sara is making a pie and needs to know the circumference of the pie dish to roll out the pastry, if the diameter is 15cm, what is the circumference? i. 50.1 cm ii. 47.1 cm iii. 45.2 cm c. In General Tech, Joe needs to make a circle with the circumference of 18.84 cm. working backwards, what is the diameter of the circle he is making? i. 7 cm ii. 9. cm iii. 6 cm

Check and correct your answers on the page named: Chapter 6.6 & 6.7 Answers

Made by Sophie Juler 7A