Answer:
As per the statement: A city has the population of 350,000 persons the population has decreased by 30% in the past 10 years.
The formula for calculating the percent change between two values over the time is given by:
[tex]p = \frac{A-B}{B} \times 100[/tex]
where
p represents the percent change
A represents the New value
B represents the Old value
Since, p is the percent(decreased) = -30
Substitute the given values and solve for B;
then;
[tex]-30= \frac{350000-B}{B} \times 100[/tex]
Divide both sides by 100 we get;
[tex]-0.3 = \frac{350000-B}{B}[/tex]
By cross multiply we get;
[tex]-0.3B = 350000-B[/tex]
Add both sides B we get;
[tex]-0.3B+B = 350000[/tex]
[tex]0.7B = 350000[/tex]
Divide both sides by 0.7 we get;
B = 500,000
Therefore, the population of city 10 years ago before 305 decrease in population was 500,000
