Expert: Lynn Houston - 8/23/2008

Question
I read on a website that tundras comprise 1/7 of the earth's surface. I assumed this to mean 1/7 of the entire surface, including oceans, lakes, etc. I wanted to figure out the amount of land surface on the earth where there are tundras.

If I know that the earth's land surface is 29.2% of the total surface, how would I go about figuring out the percentage of land tundras make up?

Answer
Think about an easier example. Suppose 2/3 of the Earth's surface is land and 1/3 of the Earth's surface is is tundra. That means 1/2 of the land is tundra.  That makes total sense, right, half of 2/3 is 1/3.  The actual equation is (1/3) / (2/3) = 1/2.

% of land covered by tundra = (amount of tundra) / (amount of land)

amount of tundra = 1/7
amount of land = .292

Therefore amount of land covered by Tundra is (1/7)/.292 = 1/2.044 or
48.92% of the earth's surface that is covered by land, is covered by tundra.

Hope this makes sense.