The population is predicted to be 60,000 in 1997. This represents a 20% increase over the 1970 population. What was the population in 1970?

Answer 1

Write an equation that models this problem. The population in 1997 is 60,000 and this is a 20% increase over the 1970 population. To increase a value by 20%, you would multiply it by 1.20 because you want to keep the original value (100% or 1) and add 20% to it (.2). Let's call the population in 1970 x.

60000 = 1.20*x

This equation reads "60000 is 120% of the 1970 population."

Divide both sides by 1.20 to solve for x.

x = 50,000

This makes the 1970 population 50,000.

Answer 2

x = population in 1970

x + 0.2x represents = population in 1970 plus 20% increase = 1997 population

x + 0.2x = 60000

1.2x = 60000

x = 50000

Answer 3

60000=120% of 1970

60000/120=60000/12=5000

so the past population was 50000

Answer 4

The population is predicted to be 60,000 in 1997. This represents a 20% increase over the 1970 population. What was the population in 1970?

I go in to detail to breakdown every step. If you only needed help on certain parts I this would be a 2 step problem.

The way I look at this is we know what the population was in 1997: 60000

If this is the result of an increase by 20% from some population in 1970, lets call it x, we can write it as the following:

1.2*x = 60000 The reason we are multiplying by 1.2 instead of 0.2 is we have the original population which we can say is at 100% or 1 and it increases by 20% so 1+0.2 = 1.2

Now what is left is to do the inverse operation, divide both sides by 1.2.

Since we can't divide with a decimal, it's similar to dividing with a mixed number, we multiply both values by 10 moving the decimal over and giving us 600000/12

since 60/12 = 5 we can simplify this to 50000