Answer:
(a) $810.45
Step-by-step explanation:
You want the value of an investment of $300 earning 5% interest compounded quarterly for 20 years.
The compound interest formula tells you the value is ...
A = P(1 +r/n)^(nt)
where P = 300, r = 0.05, n = 4, t = 20.
Using the given parameters in the given equation, you find the account value to be ...
A = $300(1 +0.05/4)^(4·20) ≈ $810.45
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Additional comment
The "rule of 72" tells you the account value will approximately double in a number of years equal to 72 divided by the interest rate percentage: 72/5 = 14.4 years. After 20 years, it will be worth more than that doubled amount, $600. This only leaves one reasonable answer choice.
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