What is the distance between 2 cities? [closed]

Both Quito and Kampala lie on the Equator. The longitude of Quito is 82°30'W and that of Kampala is 37°30'E. What is the distance from Quito to Kampala? A) along the shortest surface path B) along a direct through the Earth path? Please help me visualize it with a figure. How to do it?

closed as off-topic by Joan.bdm, Mitch Goshorn, TildalWave, Donald.McLean♦Apr 13 '15 at 11:53

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "Questions about Earth science, unless directly related to phenomena observable on other celestials, Solar system in general of which Earth is a part, or as an origin of observational astronomy where its movement, local/global phenomena might affect observations and measurements, is off-topic. For more information, see the meta discussion." – Joan.bdm, Mitch Goshorn, TildalWave
If this question can be reworded to fit the rules in the help center, please edit the question. Longitudes are measured from the Greenwich meridian, so the angle between Kampala and Quito is $$\theta_\mathrm{Q} + \theta_\mathrm{K} = 82.5^\circ + 37.5^\circ = 110^\circ.$$ (remember that $0^\circ30' = 0.5^\circ$). The shortest surface path is along Equator. Since $110^\circ$ is $\frac{110^\circ}{360^\circ} \simeq 0.3$ times the circumference of Earth at Equator, the length of path A (the dashed line) is $$\mathrm{A}:\,\,d = 0.3 \times 40,075\,\mathrm{km} = 12,245\,\mathrm{km}$$
For path B (the solid line), you need a bit more trigonometry. The radius of Earth is $R = 40,075\,\mathrm{km}\,/\,2\pi = 6,378\,\mathrm{km}$. The rest will be left as an exercise.