# Homework Help: Simple Interest: Number of Years

1. Oct 21, 2017

### zak100

1. The problem statement, all variables and given/known data
An investment is made at 12.5% annual simple interest. Find the number of years it will take for the cumulative value of the interest to equal the original investment?

2. Relevant equations
V=P(1+rt)
Where V= interest on Amount
P = Principal amount
r= interest rate
t= number of years for which amount is invested

3. The attempt at a solution
Simple Interest formula is:

V=P(1+rt) Let p =10 & t=1

V= 10(1+12.5) = 135

In just one year the interest obtained is more than the Principal value. Some body please guide me. What I understand is that, I have to find the number of years in which the interest obtained & added (with previous years’ interest becomes equal to the Principal).

Zulfi.

2. Oct 21, 2017

### andrewkirk

r is 12.5%, which is 0.125, not 12.5.

3. Oct 21, 2017

### Ray Vickson

Your formula for the interest is wrong: interest = Prt, NOT P(1+rt).

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