Math Is Fun Forum

Russ101

Guest

Calculating Days Left To Target

I need help with a formula that I can't seem to work out - probably an easy one for the mathematically enlightened!!

I have a starting investment of £200

After 9 days my investment is worth £222.74, an 11.37% increase

If I have a target of £2000, how can I work out exactly how many days it will take to reach it at this rate of growth?

Thanks

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Calculating Days Left To Target

Hi Russ101;

It takes 192.438 days to reach 2000 starting with 200 at that interest rate. I used a recurrence relation to get that but by all means use the calculator Mathsisfun has a link to below it is much easier and it comes with all the necessary formulas.

Last edited by bobbym (2009-07-15 01:52:59)

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Russ101

Guest

Re: Calculating Days Left To Target

Hi bobbym,

Thanks for the reply. I am a little confused - I haven't done any significant maths formulas since I left school 8 years ago!

Any chance you could explain where you get all the numbers from? (or indeed the principal behind the formula; as I do not even know what the In function does!).

Much appreciated.

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: Calculating Days Left To Target

Also helpful: Compound Interest

and Compound Interest Calculator

---

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

Russ101

Guest

Re: Calculating Days Left To Target

Cheers guys - it all seems straight forward when doing the formula 'forwards', to see how much the target would be in x amount of days; but I was struggling when trying to turn this around to get the days from the target.

The information is very helpful - thanks again.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Calculating Days Left To Target

Thanks Mathsisfun;

I didn't know you had already done all the work. Nice calculator.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.