Find the least number of integral years in which a sum of money invest...
Given Data:
Compound Interest Rate (r): 20% or 0.20
The sum of money is more than doubled.
Concept:
The formula for compound interest is A = P(1+r/n)(nt), where P is the principal amount, r is the annual interest rate, n is the number of times interest is compounded per year, t is the time the money is invested for in years. When compounded annually (n=1), this simplifies to A = P(1+r)t.
Solution:
We know that the formula for compound interest, when compounded annually, is A = P(1 + r)^t. Here, we want to find the smallest whole number for time t so that A > 2P.
Substituting A as 2P and r as 0.20 into the formula, we get, ⇒ 2 = (1 + 0.20)t ⇒ 2 = 1.20t
We can now try different values for t until we reach a number where 1.20t > 2.
Using t = 1, we get 1.201 = 1.20 which is not greater than 2.
Using t = 2, 1.202 = 1.44 which is not greater than 2.
Using t = 3, 1.203 = 1.728 which is not greater than 2.
Using t = 4, 1.204 = 2.0736 which is greater than 2.
Therefore, the least number of complete years in which a sum of money put out at 20% compound interest will be more than doubled is 4 years.