How to find the no of years in which population of both.the cities become equal?

Question

City A' s population is $96000$ and it is decreasing by $800$ per year and city B' s population is $68000$ which is increasing by $1200$ per year. After how many years population of both the city becomes equal? If I have to solve this question in less than 1 minute what I have to do?

Answer 1

Hint $$96000-800x=y$$$$68000+1200x=y$$

Now solve for $$x=?,y=?$$

In x years, they will both have y people

Answer 2

Create two equations for the population per year for City A and City B. Use a variable like $n$ for the year and then set these two equation equal to each other (in other words same population) and solve for $n$.

Answer 3

The simple approach is to note that they start $28000$ apart and the difference decreases by $2000$ per year. You just have to divide $\frac {28}2=14$ to get the answer.