Solving for rate in compound interest problem?

The formula for Amount = Principal(1+r/100)^t

Use this formula for determining the rate of interest

Amount/Principal = (1+r/100)^t

Now find the t th root of the quotient on L.H.S

Then solve for r

Let the Amount=12544, Principal=10000 and term=2

12544/10000 = (1+r/100)^2

1.2544 = (1+r/100)^2

take Sqaure root of both sides

1.12 = 1+r/100

r/100 = 1.12-1

r/100 = 0.12

r=12

Rate of interest = 12% per annum and the interest is compounded annullay.

In case the interest is NOT compounded annually, the r and t are to adjusted.

For example if the interest is compounded half yearly, then r shall be taken as r/2 and t shall be taken as 2*t

Additional details:

54000 = 25000(1+r/100)^10

54000/25000 = (1+r/100)^10

2.16 = (1+r/100)^10

Take 10th root on both sides of the equation

(Use scientific calculator OR logarithms OR computer)

1.08 = 1+r/100

r/100 = 1.08-1

r/100 = 0.08

r = 8%

How To Solve Compound Interest

first you need the formula which is

A = P(r/100 + 1)^n

A= end amount

P = Principle/initial amount

r = rate

n = period

it would also help us if we know what the calculations are, so we can help you better

i did a quick search, and here's what i came up with

r= nroot (A/P) - 1

so in words

it is you use the power to root the answer (e.g. if the time is 3 years, you cube root it, if the power is 6 years, you 6 root it) then in brackets you do the end amount over the initial then minus 1

or go to this website, where i learnt it

http://www.teacherschoice.com.au/maths_library/mon...