Exploring maths through problem solving

Problem of the Week

Equator through Ecuador

This photo shows equator in Ecuador, South America. The equator meets the coast of Ecuador at 80°4’ W; Gabon at 9°16’ E; Brazil at 51°3’ W; and Somalia at 45°1’ E.

Which continent has the longest length of the equator within it? What is this length?


From the map you can see that the longest segments of the equator (the red line) going through land, are from the coasts of Gabon to Somalia in Africa, and from the coasts of Ecuador to Brazil in South America.

These distances can be compared by comparing the differences in longitude along the equator, this being a circumference of the earth.

Imagine the point at the centre of a sphere with a radius drawn to each of two locations on its circumference. The further apart these two locations are, the larger will be the angle at the centre of the sphere.

Africa: The angle is from 9°16’ E (Gabon) to 45°1’ E (Somalia).

This is an angle of 45°1’ - 9°16’ = 35°45’.

South America: The angle is from 80°4’ W (Ecuador) to 51°3’ W (Brazil)

This is an angle of 80°4’ - 51°3’ = 29°1’

The continent with the longest length of the equator within it is Africa.

The circumference of the earth (360°) is about 40 000 km, so each degree along the equator is an arc with a length of about 40 000/360 = 111 km.

35°45’ = 35.75°. The distance is about 35.75 x 111 km = 3968 km.



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