Suppose a runner completes a 100-meter dash in 17.8 seconds during her first race. In the second race, she runs the 100-meter dash in 16.9 seconds. Find the percent decrease in her time. Round your answer to the nearest whole percent.

We know that the runner completed her first race in 17.8 seconds and that she completed her second race in 16.9 seconds. Then the difference between the first race and the second race is. 9 seconds. Now we divide. 9 by 17.8 and multiply by 100 to get the percent decrease. We get 5.06%. The percent decrease in her time is 5%.