# Recurring Deposit interest rate formula?

I want to find the rate of interest of a recurring deposit. suppose monthly inst. is Rs. 100, period is 24 months and maturity amount is Rs 2609. I want to find the Rate of interest. I want to know the formula for this. (Remember interest is quarterly compounded)

100 * (1 + r/4)^8 = 2609

Solve for r to get a rate of 2.01 = 201% p.a.

I don’t think i read the question right.

I’m lookin properly at it now. You want deposits added at the start of every month correct?

If that’s the case you’re solving an equation such as:

(1 + r/4)^8 + … + (1 + r/4)^1 = 26.09

Not sure how you solve that one…

Just checked: someone else agreed with me, good luck

solving that without a computer

Check this out:

http://en.allexperts.com/q/Basic-Math-657/Compound-Interest-Rate.htm

Hey I think Biglildan is correct.

i= 100

n=2yrs

r=?

a= 2609

p= 2609 – 100 = 2509

i = p*n*r

100

100 = 2509*2*r

100

100*100=2509*2

r= 1.99282583

monthly instalments compounded quarterly sounds very strange. its easier to work with a monthly interest rate, and then adjust using 1+quarterly = (1+monthly)^3

let g = 1+r where r = monthly interest rate

assuming deposits at the start of each month

your first 100 accumulates to 100 g^24

… you last 100 accumulates to 100 g^1

so you have 100 g ( 1 + g + .. + g^23) = 100 g (g^24-1) / (g-1)

which should be 2609

so 100 (g^25 – g) = 2609 (g-1)

or g^25 – 27.09g +26.09 = 0

You cant solve this algebraically, but you can do it by successive approximation or other numerical methods.

R=100/PN N = 8*8+1

The general formula for compound interest is

A = P[1 + (R/100)]^N when interest is calculated yearly basis

In the above case the interest is calculated quarterly therefor the effective rate is r = R/4

and the effective period = 2 Ã— 4 = 8

Principle = 100 Ã— 24 = 2400

2609 = 2400 [1 + (R/400)]^8

or 2609/2400 = [1 + (R/100)]^N

1.0871 = [1 + (R/100)]^N

1.010493879 = [1 + (R/400)]

1.010493879 â€“ 1 = (R/400)]

or 0.010494 = R/400

R = 0.010494 Ã— 400 = 4.1976 = 4.2 %

The following website will provide you the exact answer you are looking for, just insert the values that you know. I started by entering an assumed interest rate of 2.5 % and finally ended with an actual value of 3.95% by incrementing it by 0.1 or 0.05 etc. Assuning that you started with 100 and deposited 100 thereafter every month for two years and your final value was 2609.

Hope this helps.

http://www.debtrelief.com.au/int-calc.php

Hi,

I have master degree in mathematics and I have got thirteen ten years of teaching experience in Math at college level and currently I am working as a lecturer for an army engineering college author of math guide

contact me for solution .

thankyou