The formula is principal x ( 1+ interest rate)^ number of years
5%:
20,000 x 1.05^3 = $23152.50 total
Interest = 23152.50-20000= $3,152.50
10%
20000 x 1.10^3 = $26,620.00
Interest = 26620-20000 = $6,620
12%
20000 x 1.12^3 = $28,098.56
Interest = 28098.56-20000 = $8.098.56
