Question

the distance between two successive parallels of latitudes is 111 km. explain

Answer 1

For instance let's take the parallels Equator and Tropic of Cancer. The distance between them will be 111 km. That is the same for all other parallels of latitudes.

Answer 2

Earth represents 360° and the circumference of the Earth is approximately 40000 km.
Thus 40000/360 = 111 km
So the distance between two successive parallels of latitudes is 111 km