A rectangle is placed around a semicircle as shown below. The width of the rectangle is 4mm. Find the area of the shaded region.

Formulas:

Area_semicircle = Πr2/2

Area_rectangle = lw

Given:

Semicircle is engraved in the rectangle

length_rectangle = 8

Assumption:

Diameter of semicircle is equivalent to length of rectangle

diameter_semicircle = length_rectangle

diameter_semicircle = 8

Based on assumption, radius_semicircle is equal to the width of the rectangle.

diameter_semicircle/2 = radius_semicircle

radius_semicircle = 4 = width of rectangle

Solve:

Area_rectangle = l*w = 4*8 = 32

Area_semicircle = Πr2/2 = Π (4) 2/2 = 8Π = 25.12

Area_rectangle - Area_semicircle = 32 - 25.12 = 6.88