Percent - XYZ Custom Plus

354Chapter 5 PercentApplications of Percent [5.3, 5.4, 5.5, 5.6]There are many different kinds of application problems involving percent. Theyinclude problems on income tax, sales tax, commission, discount, percentincrease and decrease, and interest. Generally, to solve these problems, werestate them as an equivalent problem of Type A, B, or C from the previous page.Problems involving simple interest can be solved using the formulaI = P ⋅ R ⋅ Twhere I = interest, P = principal, R = interest rate, and T = time (in years). It isstandard procedure with simple interest problems to use 360 days = 1 year.COMMON MISTAKES1. A common mistake is forgetting to change a percent to a decimal whenworking problems that involve percents in the calculations. We alwayschange percents to decimals before doing any calculations.2. Moving the decimal point in the wrong direction when converting percentsto decimals or decimals to percents is another common mistake.Remember, percent means “per hundred.” Rewriting a number expressedas a percent as a decimal will make the numerical part smaller.25% = 0.25