Question #dba1a

1 Answer
Feb 21, 2017

Answer:

The population 2 years hence was 2000 people.

Explanation:

For each year, the end population is 90% of the starting population (100%). That means that:
#1620=90%#
and
#x=100%#

So, to know the population from a year ago, we have to set up the following equality:
#1620/x=90/100#

Now, with a little algebra we do the following steps to single out #x#"

1) multiply each side by #x#
#cancel(x)*1620/cancel(x)=90/100*x#

2) multiply each side by 100
#100*1620=x*90/cancel(100)*cancel(100)#

3) multiply each side by #1/90#
#1/90*100*1620=x*cancel(90)*1/cancel(90)#

Leaving us with:
#x=(100*1620)/90# which is equal to #1800#

Now if we do the same process with 1800 to start with, we get the final equation:
#x=(100*1800)/90# which is equal to #2000#