A sum of money becomes 3 times of itself in 20 years. Find its rate of interest?
if simple interest, then
1+20r = 2
r = 1/20 = 5%
if compound interest,
(1+r)^20 = 2
r = .035 = 3.5%
1+20r = 2
r = 1/20 = 5%
if compound interest,
(1+r)^20 = 2
r = .035 = 3.5%