Compound interest formula
where
• A: final amount, in dollars
,
• P: principal, in dollars
,
• r: interest rate, as a decimal
,
• n: number of times interest is compounded per year
,
• t: time, in years
Substituting with P = $20,000, r = 0.05 (=5/100), n = 4 (quarterly means that the interest is compounded 4 times per year), and t = 3/4 years, we get: