Worked example 1 A circle has a circumference equal to 6 π cm. Find (i) the diameter of the circle (ii) the area of the circle. Give your answer in terms of π.
Solution (ii)
Worked example 2 A circle has an area of 81 π c m 2
. Find (i) the radius of the circle (ii) the circumference of the circle, to two decimal places. Solution (ii)
When you are not given a value for π , use the π button on your calculator.
You should be familiar with Section B, Unit 16 before beginning the questions below.
Practice questions 29.1 3
1. Choosing from the following words, name the labelled parts of the circle shown: circumference, centre, radius, diameter
2. (i) Estimate the area of the circle on the right by counting the unit squares.
(ii) Check your answer to part (i) by calculating the area using the formula.
4 1 2
3. Find (i) the circumference and (ii) the area of the circle pictured on the right, rounding your answer to three signifi cant fi gures.
4. Find (i) the circumference and (ii) the area of the circle pictured on the right, rounding your answer to one decimal place.
5. A circle has a radius of 2·8 cm.
Taking π = 3·14, fi nd (i) the circumference and (ii) the area of the circle, rounding your answers to two decimal places.