Exercises: Circumference and Area of a Circle

Work through each section in order. Use $\pi = \frac{22}{7}$ unless told otherwise, and always write the correct unit with your answer.

Grade 7·20 problems·~27 min·Uganda NCDC Primary 7 Mathematics·lesson·measurement-02

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Recall / Warm-Up

These problems review skills you already know.

What is $\pi$ ?

A letter used to represent an unknown value that changes from circle to circle

A fixed number, approximately 22/7 or 3.14, that is the same for every circle

The name for the centre point of a circle

$Circle with centre O and radius labeled 7$

A circle has the radius shown below. Find its diameter.

A rectangle measures 6 cm by 3 cm. Find its area, to review before we look at circle area.

A circle has radius 7 cm. Find its circumference. (Use $\pi = \frac{22}{7}$ .)

A circle has diameter 28 cm. What is its circumference? (Use $\pi = \frac{22}{7}$ .)

$44$ cm -- multiply the radius (14) by $\pi$ , using only half the width

$88$ cm -- multiply the full diameter (28) by $\pi$

$616$ cm -- square the diameter and multiply by $\pi$

A circle has radius 7 cm. Find its area. (Use $\pi = \frac{22}{7}$ .)

A circle has diameter 14 cm. What is its area? (Use $\pi = \frac{22}{7}$ .)

$616$ cm² -- square the diameter (14) directly and multiply by $\pi$

$44$ cm² -- multiply $\pi$ by the diameter, forgetting to square anything

$154$ cm² -- halve the diameter to find the radius (7), then square that radius before multiplying by $\pi$

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