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June 15, 2022 Circl es 2. The area of a circle. Next

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Page 1: Circles area

April 13, 2023

Circles

2. The area of a circle.

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Page 2: Circles area

April 13, 2023

Here is a circle.You can divide it into sectors.The sectors can be rearranged, to form a shape very close to a rectangle.The two long edges are made up from the circumference, which is π

× d

One side is made up from π

× d which is π

× rEach of the short sides is made up from the radius.

÷ 2

r

π × r

The area can now be calculated as π

× r × r or π r ²

Explanation

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Page 3: Circles area

April 13, 2023

The second hand on a clock is 11cm long.What is the area of the clock face it passes over in one minute?

A = πr ²

A = π × 11²

A = π ×

A =

121

380.1327…

The area the second hand covers is is 380cm², to 3 s.f.

In this case, it is sensible to give an answer to the nearest cm ².

Example

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Page 4: Circles area

April 13, 2023

A circular office carpet has a diameter of 1.8m.Calculate its area. A = πr ²

r = 1.8 ÷ 2 = A = π × 0.9²

A = π ×

A =

Calculate the radius.

The carpet is 2.54m², to 2 d.p.

0.9

0.81

2.54690…

Example

It is sensible to give an answer to the nearest cm².

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