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#1 2011-04-12 05:52:39

survival
Member
Registered: 2011-04-03
Posts: 655

Compound Interest

Hello,
If I save $85.00 in a savings account with 6% interest which compounds monthly, how much money will I have after 1 yr/ 10 yrs./ 20 yrs. and 30 yrs. This is by a formula of A = P (1 + r/m) n. I did not know how to get that n up to the top of the last part of the formula.)
Thank you!

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#2 2011-04-12 06:34:54

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest


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.

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#3 2011-04-12 06:54:56

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

thank you, bobbym.

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#4 2011-04-12 06:57:03

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

Hi;

I thought that once you see it actually working then if you want we can over some of it. Seeing something work is a good way of eliminating the age old question of what is it good for.

Want to do one by hand with me?


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.

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#5 2011-04-12 08:13:30

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

if i do this on my calculator it does not come out like that site. i have  $98.00 (sorry i added the first wrong)

98 x 12 =1176 total money to start with the first year.
98x 6(%) x 12 (months)=7056. Is that the total savings with 6%?

then 98 x that amount for 10/20/30 years?

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#6 2011-04-12 08:22:19

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

Hi survival;

If you are not getting the answer there then you are probably doing something wrong.


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.

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#7 2011-04-12 08:29:15

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

i do not mean to but it is that way

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#8 2011-04-12 08:30:29

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

It is okay. Please restate your problem with the new figures you want to use.


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.

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#9 2011-04-12 08:44:07

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

98 dollars (98.00)
the account has 6% interest which compounds monthly, how much money would i have after 1 yr.? 10 yrs? after 20 yrs? after 30 yrs?

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#10 2011-04-12 08:45:39

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

Do you deposit money each month into the account?


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.

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#11 2011-04-12 08:52:41

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

it is class. i have the problem to figure out.

the 98.00 is the amount i am supposed to have in my account.
the 6% is the rate that compounds monthly and they want to know how much i will have after 1, 10, 20 and 30 yrs.

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#12 2011-04-12 08:54:13

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

yes it looks like it goes in there every month.

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#13 2011-04-12 08:55:37

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

So you are depositing 98 dollars per month.


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.

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#14 2011-04-12 08:59:21

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

yes so it is $98.00 X 12 (1 yr.)=$1, 176.00 before any compounded interest

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#15 2011-04-12 09:00:28

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

Yes, please hold now while I do some calculating.


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.

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#16 2011-04-12 09:11:04

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

thank you

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#17 2011-04-12 09:17:25

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

Okay and bear with me, I am the worst with financial calculations. I only have 47 bucks in my checking account so...

I am getting $ 1312.929 Now I imagine that banks will round down to $1312.92 rather than round up to $1312.93


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.

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#18 2011-04-12 09:23:46

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

is this for one year? or 10 years?

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#19 2011-04-12 09:30:04

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

1 year.


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.

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#20 2011-04-12 09:34:16

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

thank you

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#21 2011-04-12 09:35:31

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

Please check it. Get back to me when you do.


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.

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#22 2011-04-12 09:37:58

survival
Member
Registered: 2011-04-03
Posts: 655

Re: Compound Interest

i will. i am working on 3 more class homework today besides this one

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#23 2011-04-12 09:40:05

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

Yikes! Home work as you can see is made up of 2 four letter words and should be outlawed.


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.

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#24 2011-04-12 19:25:31

Bob
Administrator
Registered: 2010-06-20
Posts: 10,621

Re: Compound Interest

hi survival and bobbym,

This looks like the problem

http://www.mathisfunforum.com/viewtopic.php?id=15166

But I'm not sure if the interest rate is 6% per month (ok but seems rather generous in the current economic climate) or 6% per year.

So I've used Ad's spreadsheet with $98 instead of £100 and used both rates.  see below The first is 6% per month; the second is 6% per year.

Bob


Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob smile

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#25 2011-04-12 20:22:14

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: Compound Interest

Hi Bob;


I used a recurrence relation. This gets the same answer.

http://illuminations.nctm.org/ActivityD … spx?id=172

Put in a principal of 98 and monthly additions of 98. 1 year ( it is compounded monthly ) at 6 %.


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.

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