In 2015 China consumed oil at a rate of about 11 million barrels per day, which was increasing by 8% annually. The United States consumed about 19 million barrels per day, with little change from year to year. If these trends hold, how long before China overtakes the United States in oil consumption?

It will take 7 years and 37 days.

Explanation:

Giving the following information:

In 2015 China consumed oil at a rate of about 11 million barrels per day, which was increasing by 8% annually. The United States consumed about 19 million barrels per day, with little change from year to year.

Because we don't have the growing rate of the United States, we will remain 19 million unchanged.

We need to use the following formula:

fv = pv * (1+i) ^n

Isolating n:

n=[ln (FV/PV) ]/ln (1+r)

n=ln (19,000,000/11,000,000) / ln (1.08)

n = 7.10

To be more accurate:

0.10*365 = 37 days

It will take 7 years and 37 days.