Final answer:
The formula for compound interest is a = p(1 + rt). In this case, the teacher puts $300 into a savings account for 12 years. The solution for r is r = a/300 - 12.
Step-by-step explanation:
The formula for compound interest is given by the equation:
a = p(1 + rt)
Where:
- a is the final amount after time t
- p is the initial principal (amount)
- r is the annual interest rate (expressed as a decimal)
- t is the time in years
In this case, the teacher puts $300 into a savings account for 12 years. To determine the solution for r, we need to rearrange the formula:
r = (a/p - 1)/t
Substituting the given values:
r = ($300/a - 1)/12
Therefore, the correct answer is C) r = a/300 - 12.