Note: We refer to the perimeter of a circle as the circumference of a circle. A circle is a perfectly
round plane figure in which every point on its circumference is equidistant from its centre.
(“Equidistant” means the same distance from the centre of the circle.)
, We call the distance from the centre (m) to the circumference the radius (r) of the circle. The
diameter (d) is the straight line from side to side passing through the centre (m). The diameter (d) is
two times as long as the radius (r), therefore d = 2r.
The formula for the circumference (C) of a circle is C = 2∏r.
We know that the diameter is two times as long as the radius (diameter = 2 x radius).
The perimeter of a semicircle is half of the circumference of a full circle.
Therefore, the perimeter is calculated as follows:
𝐶 = 2𝜋r
=2𝑥𝜋𝑥2
≈ 12,57
(On SHARP EL-738F press 2 𝑥 𝜋 𝑥 2 =)
As this is a semi-circle we will divide the answer by 2:
12,57 ÷ 2 = 6.28 cm
Solution:
6cm + 4.8cm + 2cm + 6cm + 6,28 = 25.08
Calculate the area of a triangle with base 44,7mm and height 10mm.
The area of a triangle is
1
A = 2𝑏 𝑥 ℎ
1
= 𝑥 44,7 𝑥 10
2
≈ 223,5
The area of the triangle is 223,5mm2.
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