Multiply the rate of change by 100 to convert it to a percent change. In the example, 0.50 times 100 converts the rate of change to 50 percent. However, if the numbers were reversed such that the population decreased from 150 to 100, the percent change would be -33.3 percent. So a 50 percent increase, followed by a 33.3 percent decrease returns the population to the original size; this incongruity illustrates the 'end-point problem' when using the straight-line method to compare values that may rise or fall.
The Midpoint Method.
The percent change equation only compares two values at a time. This means that if you're asked to calculate percent change in a situation involving a variable with multiple value changes, only calculate the percent change between the two values specified. To calculate the percentage change in nominal GDP, start with the GDP from the previous year and divide it by the same number, then multiply that by the same number. The sum is the percentage.
Like solving for distance, solving for time involves rearranging the speed equation. But this time there are two rearranging steps instead of one. To get t alone, you must first multiply both sides by t, then divide both sides by s. Now t will be alone on the left side of the equation: t = d ÷ s Imagine the car travels 350 miles at an average speed of 65 miles per hour and you want to know how long the trip took.
Plug the values for distance and speed into the newly rearranged equation: t = 350 miles ÷ 65 miles/hour = 5.4 hours.