The city of Carterville measures its population every year as of April 1st of that year. The table above shows the year-to-year percent growth of the population of Carterville from 2014 to 2016. If the population of Carterville was 1,059,382 on April 1, 2013, which of the following could have been the population on April 1, 2016 ?A)1,153,120B)1,145,489C)1,123,894D)1,086,296 Loading... Page navigation ← Daily PWN 013 Daily PWN 015 →

Why can’t this short method work… Total population growth =3.2+2.8+2.6=8.6% In April 2016: 1,059,382 * 1.086…. I get an answer close to answer choice B. Log in to Reply

You can’t just add growth rates to come to a total growth rate because the growth rates compound. Watch what happens if you grow 100 by 2% 20 times vs growing 100 by 40% (the sum of 2% added 20 times). 100*1.02^20 = 148.59… 100*1.4 = 140 Log in to Reply

## Comments (2)

Why can’t this short method work…

Total population growth =3.2+2.8+2.6=8.6%

In April 2016: 1,059,382 * 1.086….

I get an answer close to answer choice B.

You can’t just add growth rates to come to a total growth rate because the growth rates compound.

Watch what happens if you grow 100 by 2% 20 times vs growing 100 by 40% (the sum of 2% added 20 times).

100*1.02^20 = 148.59…

100*1.4 = 140