Calculate Percent Change
Problem: The population of a particular city increased from
400,000 to 500,000. Determine the percent change in
the population.
Key Concept: When determining the percentage of change,
compare the amount of the change to the original
quantity.
For this problem, the amount of change was 100,000
people. The original population was 400,000.
To determine the percent change , divide the amount of
change by the original quantity. So we say:
100000  400000  .25
Remember, when changing from a decimal to a percent, we
move the decimal two places to the right. So:
. 𝟐𝟓 = 𝟐𝟓%
The population changed by 25%.
Just for thought:: If the population had changed from
500,000 to 400,000, we would have divided the
amount of the change (100,000) by the original
population (500,000) and determined that the
population decreased by 20%