Any mathematicians in the house, please?

[ThinkOutsideTheBox]

It sounds quite straightforward, but my brain wont engage.

I'm looking to calculate the amount of interest on a sum of money owing, when that sum of money is increasing on a daily basis over a period of 6 months (well, it increases 5 days out of 7, but interest would accrue 7 days out of 7). The interest shouldn't be compounded.

To give an example of how the amount owing increases -


1st October 2013 - Amount owing £0.00
2nd October 2013 - £3.15
3rd October 2013 - £6.30
4th October 2013 - £9.45
5th October 2013 - £12.60
6th October 2013 - £12.60
7th October 2013 - £15.75
8th October 2013 - £15.75
9th October 2013 - £18.90

The amounts given are a running total, excluding any interest. As you can probably see, the debt increases by an amount of £3.15 each day (excluding Tuesdays and Sundays)


Need to calculate the total amount owing as at 11th April 2014, based on an interest rate of 8% and the interest not being compounded.


Any suggestions?

Thank you in advance.

[wales01man]

Re: Any mathematicians in the house, please?

Excuse my ignorance but how can a balance of nothing incur interest?

[ThinkOutsideTheBox]

Re: Any mathematicians in the house, please?

Sorry, perhaps not clear. I only included the balance at 1st October to show that there was nothing owing prior to 2nd October.

The increase in the amount owing each day as shown above has nothing to do with interest, that's an increase of the capital amount owing which continued to increase between 1st October and 11th April. Interest hasn't been taken into consideration at all yet.

[wales01man]

Re: Any mathematicians in the house, please?

My brain hurts thinking on this one sure someone can help

[ThinkOutsideTheBox]

Re: Any mathematicians in the house, please?

Haha, glad I'm not the only one! I'm usually good with numbers, but this one is just a jumbled mess.

Thanks for taking a look though, appreciate it.

[got no money]

Re: Any mathematicians in the house, please?

hi
i get £447.30 that is 28 weeks x 5 day per week @ £3.15 per day (which takes to 9/04/14 ) +£6.30 for 10/11 0f april =£447.30

[ThinkOutsideTheBox]

Re: Any mathematicians in the house, please?

That bit I can manage.

I now want to be able to calculate the interest on that increasing balance, at a rate of 8% per annum, which accrues each day but is simple rather than compounded.

That's where I get lost, lol.

[got no money]

Re: Any mathematicians in the house, please?

That bit I can manage.

I now want to be able to calculate the interest on that increasing balance, at a rate of 8% per annum, which accrues each day but is simple rather than compounded.

That's where I get lost, lol.

well the simple way would be for example if you deposited say 400.00 interest @ 8% per annum = £32.00 divide by 365 =0.08p interest per day sorry if i have read your question wrong

[ThinkOutsideTheBox]

Re: Any mathematicians in the house, please?

The difference is that on each day the amount owning is different, therefore the interest amount is different.

Only on 11th April 2014 will interest be chargeable on the full total of £447.30, so on that day 9.8p would be the interest charge.

On 5th October 2013 for example, the outstanding balance was £12.60, so on that day only 0.27p would be the interest charge.

If it was a steady balance each day then it would be easy to calculate (like a fixed deposit amount), and if it was a balance which increased by the same amount every single day then I could come up with a formula to do it...it's the fact that it's an increasing balance, but only increases 5 days out of 7 and accrues interest 7/7 that is throwing me. Just can't make sense of it in my head to come up with a logical way of calculating. :noidea:

[got no money]

Re: Any mathematicians in the house, please?

The difference is that on each day the amount owning is different, therefore the interest amount is different.

Only on 11th April 2014 will interest be chargeable on the full total of £447.30, so on that day 9.8p would be the interest charge.

On 5th October 2013 for example, the outstanding balance was £12.60, so on that day only 0.27p would be the interest charge.

If it was a steady balance each day then it would be easy to calculate (like a fixed deposit amount), and if it was a balance which increased by the same amount every single day then I could come up with a formula to do it...it's the fact that it's an increasing balance, but only increases 5 days out of 7 and accrues interest 7/7 that is throwing me. Just can't make sense of it in my head to come up with a logical way of calculating. :noidea:

its not 0.27p its was 0.0027p so not even a penny interest on 5/10/13

[ThinkOutsideTheBox]

Re: Any mathematicians in the house, please?

That's what I said, 0.27p, not £0.27.

Precisely why I can't just assume the whole 8% interest on the total balance over the course of the 28 weeks, as the amount accrued each day varies considerably.

[Turboman]

Re: Any mathematicians in the house, please?

Its a bit hard to help precisely without you saying where and what these charges are for

However--I have assumed they are some sort of PENALTY incurred daily of £3.15--except on Tuesdays & Sundays for some odd reason.

You are after the simple interest of 8 %.
The way to do this is to calculate the number of days that have elapsed since EACH SEPARATE CHARGE to the date you want the calculation to--and multiply by the daily interest rate of 8%/365 { in practice I have used .00022p per day which is accepted by the courts)

On the enclosed spreadsheet I have effectively entered every date from 2/10/13 to 11/4/2014 inclusive
This results in 192 days @ £3.15 per days penalty but excluding Tuesdays and Sundays--resulting on a total of £434.70 in Penalties

The Interest at 8% on EACH SEPARATE CHARGE is shown in the last column and totals a mere £12.21 as of the date in red of 13/5/2014--change it if you want earlier date

Hope I have understood your requirements--if not let me know--Spreadsheet follows:

TOTB-v2.xls

[Guest]

Re: Any mathematicians in the house, please?

Who was that masked man ?

[Turboman]

Re: Any mathematicians in the house, please?

Hmmm---don't understand that comment?----Please explain

Only trying to help

Who was that masked man ?

[FlamingParrot]

Re: Any mathematicians in the house, please?

Hmmm---don't understand that comment?----Please explain

Only trying to help

That makes 2 of us...