Answer :
13%
Step-by-step explanation:
Compound interest which is compounded annually calculated using the formula :
A = I( 1 + r/100)^t
Where I = invested amount
r = interest rate ; t = period ; A = final amount
If period = 9years, the rate required to triple the investment equals;
The final amount = 3 * invested amount = 3I
We now have ;
3I = I( 1 + r/100)^9
Divide both sides by I
3 = (1 + r/100)^9
Take the 9th root of both sides
3^(1/9) = (1 + r/100)^(9*1/9)
3^(1/9) = 1 + r/100
r/100 = 3^(1/9) - 1
r/100 = 1.1298309 - 1
r / 100 = 0.1298309
Multiply both sides by 100
r = 12.98309
r = 12.98 = 13%
