Question

Easy Bank offers you a monthly interest rate of 0.30% for deposits, how long does it take to

a) double your money in years?

b) To triple it in years?

Answer 1

FV = PV * (1 + r)^n

(1 + r)^n = FV/PV

n * ln(1 + r) = ln(FV/PV)

n = ln(FV/PV)/ln(1 + r)

a. FV = 2

PV = 1

r = 0.30%

n = ln(FV/PV)/ln(1 + r)

n = ln(2/1)/ln(1 + 0.0030)

n = ln(2)/ln(1.0030)

n = 0.6931471806/0.00299550898

n = 231.3954607474 months

Or it takes 231.3954607474/12 = 19.2829550623 Years for the money to double.

b. FV = 3

PV = 1

r = 0.30%

n = ln(FV/PV)/ln(1 + r)

n = ln(3/1)/ln(1 + 0.0030)

n = ln(3)/ln(1.0030)

n = 1.0986122887/0.00299550898

n = 366.7531281111 months

Or it takes 366.7531281111 * 12 = 30.5627606759 years for the money to triple