Comparing financial options involves translating percentage rates, per-unit rates, fixed fees, and transaction charges into a common basis, such as the total cost or amount earned for the same amount of money and time. Tables, equations, graphs, and unit rates reveal how fees affect the comparison and why a lower stated rate may not mean a lower overall cost; compound interest, variable-rate models, taxes, and formal APR calculations are beyond this scope.
To compare financial options fairly:
You have 200$ to save for one year.
Which bank gives you more money after one year?
Convert each percentage to a decimal and multiply by 200$.
Bank A:
Bank A earns 6$ interest.
Bank B:
Bank B earns 5$ interest.
Bank A charges 4$, so its net earnings are:
Bank A gives you 2$ in earnings after the fee.
Bank B has no fee, so its net earnings are:
Bank B gives you 5$ in earnings.
| Bank | Interest earned | Fee | Net earnings |
|---|---|---|---|
| A | 6$ | 4$ | 2$ |
| B | 5$ | 0$ | 5$ |
Bank B is the better choice, even though its stated interest rate is lower. The fee makes Bank A’s total earnings smaller.
The key idea is to compare the final cost or earnings on the same amount of money for the same length of time.
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