7,279,009,630 people and counting

GMAT question of the day, sentence correction
What’s the antecedent of Mexico and the U.S.? Laurasia? – GMAT Sentence Correction
December 3, 2014
QOD2014_128
Data Sufficiency from every corner of the globe
December 8, 2014
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7,279,009,630 people and counting

QOD2014_125
Explanation
Let the country's initial population be 1.
We want to find when the population will be more than 1.5*1 = 1.50.

Population is growing at 10% per year.

After one year, the population would be: 1*(1 + 10%) = 1*1.1=1.1.

Similarly, after two years, the population would be 1*(1.1)2 = 1.21 < 1.50.

Again, after four years, the population would be 1*(1.1)4 = ~1.44 < 1.50.

After five years, the population would be 1*(1.1)5 = ~1.44*1.1 < 1.50.

We do not need to proceed: Looking at ~1.44*1.1, we can be sure that the product would be more than 1.5.

The correct answer is C.

At the time of this post, the world’s population is 7,279,009,730. This counter allows you to see the world’s population grow in real-time.  The UN has predicted that the world’s population will include 8 billion people by 2025. By 2050, we will have added another billion.