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Circles - Using π - Level 3

Practise using pi to calculate various circle measurements.

Level 1 Level 2 Level 3 Level 4 Level 5 Level 6 Exam-Style Description Help

This is level 3; find the area of a circle given either the radius or diameter. Give your answers correct to three significant figures. You can earn a trophy if you get at least 7 correct. The diagrams are not drawn to scale.

Diagram 1
The radius of this circle is 7cm.

Calculate the area of the circle in square centimetres.

Don't forget to round off your answer to three significant figures.

cm² Correct Wrong

Diagram 2

The radius of this second circle is 7.7cm.

Calculate the area of the circle.

cm² Correct Wrong

Diagram 3

The radius if this circle is 5cm.

Calculate the area of the circle.

cm² Correct Wrong

Diagram 4

It is the diameter that is given for this circle, not the radius. Calculate the area of the circle if its diameter is 18cm.

cm² Correct Wrong

Diagram 5

The diameter of this circle is 7.2cm.

Calculate the area of the circle.

cm² Correct Wrong

Diagram 6

Calculate the area of this circle.

cm² Correct Wrong

Diagram 7

Four identical circles fit exactly inside a square as shown in the diagram. Each side of the square is 9.3cm.

Calculate the total area of all four circles.

cm² Correct Wrong

Diagram 8

A circle is cut out of a square. Each side of the square is 8.8cm.

Calculate the area of the remaining purple area when the circle has been removed.

cm² Correct Wrong



The diameter of a circle is 7.9cm longer than its radius.

Calculate the area of the circle.

cm² Correct Wrong



The circumference of a circle is 89.9cm.

Calculate the area of the circle.

cm² Correct Wrong

Check

This is Circles - Using pi level 3. You can also try:
Level 1 Level 2 Level 4 Level 5 Level 6 Composites

Instructions

Try your best to answer the questions above. Type your answers into the boxes provided leaving no spaces. As you work through the exercise regularly click the "check" button. If you have any wrong answers, do your best to do corrections but if there is anything you don't understand, please ask your teacher for help.

When you have got all of the questions correct you may want to print out this page and paste it into your exercise book. If you keep your work in an ePortfolio you could take a screen shot of your answers and paste that into your Maths file.

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Description of Levels

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Level 1 - find the circumference given the radius or diameter.

Level 2 - find the radius or diameter given the circumference.

Level 3 - find the area of a circle given either the radius or diameter.

Level 4 - the areas of circles are given, find either the radius, diameter or circumference.

Level 5 - the radius and angle subtended at the centre of the circle are given, find the length of the arc or area of the sector of the circle.

Level 6 - this level has mixed questions about the circle. Most of these questions will require a multi-part calculation once the situation described in the question has been understood.

Areas of composite shapes requires an ability to calculate the areas of other shapes such as rectangles, triangles and trapezia.

Exam Style questions are in the style of GCSE or IB/A-level exam paper questions and worked solutions are available for Transum subscribers.

Answers to this exercise are available lower down this page when you are logged in to your Transum account. If you don’t yet have a Transum subscription one can be very quickly set up if you are a teacher, tutor or parent.

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Help with circle calculations

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Use a calculator for this exercise. All of the calculations you will do involve the number π (pronounced pi) which is roughly equal to 3.141592. You should use the π button on your calculator to get this number into your calculation.

Let r be the radius, d the diameter, C the circumference and A the area of a circle.

C = πd    [i.e., to find the circumference multiply the length of the diameter by pi]

A = πr2    [i.e., to find the area multiply the square of the radius by pi]

Circle attributes

For arcs multiply the circumference by the angle subtended at the centre and divide by 360.

For sector area multiply the circle area by the angle subtended at the centre and divide by 360.

For help using a calculator with circle calculations see Calculator Workout.

For more on this topic see our Circles page.

Answers to this exercise are available lower down this page when you are logged in to your Transum account. If you don’t yet have a Transum subscription one can be very quickly set up if you are a teacher, tutor or parent.

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