A car's value, in dollars, after t years is modeled by V(t) = 28,000(0.82)^t. By what percent does the car's value decrease each year?

In an exponential model $V(t) = V_0 b^t$, the base $b$ is the yearly multiplier. Here $b = 0.82 = 1 - 0.18$, so the car keeps 82% of its value each year and loses 18%. The answer is 18. A common wrong answer is 82, which is the percent that remains rather than the percent lost. Another is 0.82, which misreads the decimal as a percent. A third is 28,000, the starting value. For decay, subtract the base from 1 and convert the result to a percent.