April 13, 2023
Circles
2. The area of a circle.
NextNext
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
NextNextMoreMore
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
NextNextMoreMore
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.
EndEndMoreMoreNextNext
Top Related