perimeter = 25.71 km
Explanation:
the perimeter (P ) or circumference of a circle is
P = 2πr = πd
where r is the radius and d is the diameter
here it is a semicircle, that is half the circle
⇒ 1/2 × 2πr = πr is the perimeter
here d = 10 ⇒ r = 10/2 = 5
the perimeter of this semicircle includes the diameter
⇒ P = (π × 5) + 10
= (3.142 × 5) + 10
= 15.71 + 10
= 25.71 km
