Explanation

To find the perimeter of a semi-circle, we need to consider two parts:

1. The half of the circumference of the circle, which is $frac{1}{2} times 2pi r = pi r$.
2. The diameter of the circle, which is $2r$.

• The radius $r = 700$ meters.

1. Calculate the curved part (half of the circumference):

   $$text{Curved part} = pi times r = pi times 700 approx 3.1416 times 700 approx 2199.12 , text{m}$$

2. Add the diameter:

   $$text{Diameter} = 2 times r = 2 times 700 = 1400 , text{m}$$

3. Total perimeter:

   $$text{Perimeter} = text{Curved part} + text{Diameter} = 2199.12 , text{m} + 1400 , text{m} = 3599.12 , text{m}$$

4. Convert the result to kilometers:

   $$3599.12 , text{m} = 3.6 , text{km}$$