Problem

Simple interest I in dollars is calculated using the formulawhere p represents principal,...

Simple interest I in dollars is calculated using the formula

where p represents principal, or amount, in dollars that is invested or borrowed, r represents annual interest rate, expressed as a decimal, and t represents time, in years.

In Exercises, find the value of the remaining variable in the simple interest formula. See Example. (Hint: Write percents as decimals. See Section R.2.)

Example Using Formulas to Evaluate Variables
Find the value of the remaining variable in each formula.
(a) , L = 10
This formula gives the area of a rectangle. See FIGURE 9.
The width is 6.4. Because 10(6.4) = 64, the given area, the answer checks.
(b) , B = 27, h = 10
This formula gives the area of a trapezoid. See FIGURE 10.
FIGURE
The length of the shorter parallel side, b, is 15. This answer checks because
, as required.