Question

"From 1990 to 2000 The population of city A rose from 12,000 to 28,000 and the population of city B rose from 18,000 to 24,000. If the population of the two cities increased at a constant rate, in what year was the population of both cities the same?"

Answer 1

The year 1996

With population of both 21600

Explanation:

From 1990 to 2000 = 10 years

So city A grew from 12000 to 28000 that is city A had an increase of 16000 in 10 years.

While city b grew from 18000 to 24000 , that's an increase of 6000 in 10 years to.

For city A

10 years= 16000

1 year = 16000/10

1 year = 1600

For city B

10 years = 6000

1 year = 6000/10

1 year = 600

So we are to find what year the both cities had same population.

12000 + x1600 = y

18000 + x600 = y

X is the year difference

Y is the population at that year

Eliminating y gives

6000= x1000

X= 6

If x is 6

18000+3600= y

21600= y

So 6 years + 1990 = 1996