Question

find the rate at which a sum of money will double itself in 3 years if the interest is compounded annually

Answer 1

Let principal = P

Amount = 2P

2P = P(1+R/100)^3
2= (1+R/100)^3
2^(1/3) = 1+R/100
1.2599 = 1+R/100
1.2599-1 = R/100
0.2599×100 = R
R = 25.99 ~ 26%

Answer 2

☆☆☆Let the rate percent per annum be R.
Then,
A=P(1+R/100)^n
2P=P(1+R/100)^3
(1+R/100)^3=2
(1+R/100)=1.2599
R/100=0.2599
R=25.99
Thus, the required rate is 25.99% per annum.
#hope it helps You :D