What is the world demand for iron, if the known global reserves are 100,000,000,000 tons and the static reserve is 238?

Question

Quizplus · Accepted Answer

The static reserve is the percentage of known reserves that is currently economically recoverable. Here, the static reserve is 238 out of 100,000,000,000. To calculate the world demand for iron, we need to subtract the static reserve from the known reserves: 
100,000,000,000 - 238 = 99,999,999,762 
Therefore, the world demand for iron is about 400,000,000 tons (rounded to the nearest million), which is closest to choice B.

What Is the World Demand for Iron, If the Known