Answer:
Perimeter = 20cm ; area = 59.5cm
Explanation:
Given the following :
Perimeter of entire figure = 42cm
Diameter of circle (d) = 7cm
Find the perimeter of the circle :
The perimeter (p) of a circle equals :
2πr
Where r = radius of circle
r = diameter /2 = 7/2 = 3.5cm
Therefore,
P = 2 * (22/7) * 3.5
P = 22 cm
Looking at the figure, we only take the semicircle :
Therefore perimeter of each semicircle =
22cm / 2 = 11cm
Therefore, perimeter of the red shaded region =
(42 - 22)cm = 20cm
Area of Circle = πr^2
(22/7) * 3.5^2 = 38.5 cm
Area of each semicircle = 38.5/2 = 19.25cm
Total area of semicircle = (19.25 +19.25) = 38.50cm
To find sides of rectangle :
Perimeter of the rectangle :
width = diameter of circle = 7cm
2(l + w) = 42
2(l + 7) = 42
2l + 14 = 42
2l = 42 - 14
2l = 28
l = 28/2
length (l) = 14cm
Therefore, area of rectangle :
Length * width
14 * 7 = 98cm
Area of red portion:
Area of rectangle - (area of the 2 semicircles)
98cm - 38.50cm
= 59.50cm