Answer :
Answer:
5,697 km
Explanation:
The distance along the north-south line (longitude) is a distance along a great circle.
Given City A at 20°N, and City B at 31°S:
Step 1: Find the angular difference:
Note that since they are on a different axis, we add:
[tex]\begin{gathered} \theta=20\degree+31\degree \\ \theta=51\degree \end{gathered}[/tex]Step 2: Find the distance:
[tex]\begin{gathered} \text{Distance along a great circle}=\frac{\theta}{360}\times2\pi R \\ =\frac{51\degree}{360\degree}\times2\times\pi\times6400 \\ =5696.8\operatorname{km} \\ \approx5697\operatorname{km} \end{gathered}[/tex]The distance in kilometers between cities A and B is 5,697km (to the nearest km).