how do i work out what percentage interest has been paid knowing the amount invested and the interest paid?

Answer 1

Just divide the interest paid over the amount invested and times the answer with 100 to get the interest percentage

Answer 2

Working Out Interest Rates

Answer 3

I assume you have just invested one lump sum, as opposed to making regular payments (e.g. monthly).

I will show you how to calculate the annual interest rate you have earned.

The annual rate is a good indicator as this is what is quoted by banks for their savings accounts.

Suppose you invest a lump sum of £5,558 for 5 months and are paid £12.23 interest in total for that 5 months.

Let i = annual interest rate

You have invested for a period of 5/12 of a year ( 5 months out of 12).

This means that your:

initial investment * ( 1 + annual interest rate ) ^ (5/12)

= Initial investment plus interest earned

the ^ sign stands for "power" and is on most scientific calculators.

So in our example:


5558 * (1 + i) ^ (5/12) = 5558 +12.23
5558 * (1+ i ) ^ (5/12) = 5570.23

Then with a little rearrangement we see that:

i = (5570.23 / 5558) ^ ( 12 / 5) - 1
i = 0.00523
if we multiply that by 100

0.00523 *100 = 0.523% we get the answer.

So basically:

i = ((Investment + Interest) / investment ) ^ (12 / months held) - 1

Then multiply by 100 to see it as a percentage.

Hope that wasn't too complicated!

Make sure you use the brackets in your calculation!

Answer 4

you take the amount invested and divide it into the amount received that will give you the % . to get the annul % you need to divide the number of days in to the % then multiply 365 for the number of days in a year

Answer 5

Assuming the period is a year.

interest paid gross/investment*100

Answer 6

Calculator will work it out

Answer 7

Go back to school and learn - you will find it more satisfying.