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if you spend $2,548 a year, how much would you save after 5 years if every year you put that money into a savings account that earned 5% annual interest. 25 years? 50 years?

 Jan 4, 2015

Best Answer 

 #1
avatar+7 
+10

5%+100=105%=105/100=1.05

**without following years:

[saving - spending]*years*1.05^years=

[2548*(1.05) -2548]5*1.05^5=812.99

[2548*(1.05) -2548]25*1.05^25=

[2548*(1.05) -2548]50*1.05^50

 Jan 4, 2015
 #1
avatar+7 
+10
Best Answer

5%+100=105%=105/100=1.05

**without following years:

[saving - spending]*years*1.05^years=

[2548*(1.05) -2548]5*1.05^5=812.99

[2548*(1.05) -2548]25*1.05^25=

[2548*(1.05) -2548]50*1.05^50

ororen1909 Jan 4, 2015
 #2
avatar+118608 
+5

okay, Say you put the money in the bank at the END of each yeaar.

How much will you have at the END of 5 years.

Ok

the first deposit of $2548 will be earning 5% pa  interest for 4  years

This is how much it will grow to

$${\mathtt{2\,548}}{\mathtt{\,\times\,}}{\left({\mathtt{1.05}}\right)}^{{\mathtt{4}}} = {\mathtt{3\,097.109\: \!925}}$$

that is $3097.10

 

the second deposit of $2548 will be earning 5% pa  interest for 3  years

This is how much it will grow to

$${\mathtt{2\,548}}{\mathtt{\,\times\,}}{\left({\mathtt{1.05}}\right)}^{{\mathtt{3}}} = {\mathtt{2\,949.628\: \!5}}$$

that is $2949.63

 

the third deposit of $2548 will be earning 5% pa  interest for 2  years

This is how much it will grow to

$${\mathtt{2\,548}}{\mathtt{\,\times\,}}{\left({\mathtt{1.05}}\right)}^{{\mathtt{2}}} = {\mathtt{2\,809.17}}$$

that is $2809.17

 

the forth deposit of $2548 will be earning 5% pa  interest for 1  years

This is how much it will grow to

$${\mathtt{2\,548}}{\mathtt{\,\times\,}}\left({\mathtt{1.05}}\right) = {\mathtt{2\,675.4}}$$

that is $2675.40

 

the fith deposit of $2548 will be earning 5% pa  interest for 0  years (you only just now depositied it

So it will still be worth  $2548

 

NOW add all those together and you will see how much your deposits will grow to after 5 years.

 

$${\mathtt{3\,097.1}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2\,949.63}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2\,809.17}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2\,675.4}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2\,548}} = {\mathtt{14\,079.3}}$$

 Jan 4, 2015
 #3
avatar+128631 
+5

I believe we have an annuity here...the "formula" for the accumulated amount after "n" years is given by

A = C [ (1 + i )n - 1 ] / i   where C is the cash flow per period, i is the interest rate per period, and n is the number of periods - (in this case, years)

I'll do the first one for you.....and you can "plug and play" to arrive at the other two answers

for the accumulated amount after 5 years, we have

A = 2548 [ (1 + .05)5 - 1] / .05  = $14, 079. 31

 

 Jan 4, 2015
 #4
avatar+118608 
+5

Now if you want 25 years of 50 years you probably need to develope a formula or use one that someone else has already developed.

It it the future value of an annuity  problem.  

Use future value of an ordinary annuity with n=25 and 50 respectively 

 Jan 4, 2015
 #5
avatar+118608 
+5

2548 [ (1 + .05)5 - 1] / .05

 

$${\frac{{\mathtt{2\,548}}{\mathtt{\,\times\,}}\left({\left({\mathtt{1}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.05}}\right)}^{{\mathtt{5}}}{\mathtt{\,-\,}}{\mathtt{1}}\right)}{{\mathtt{0.05}}}} = {\mathtt{14\,079.308\: \!425}}$$

 Jan 4, 2015
 #6
avatar+118608 
+5

Good attempt ororen1909  but you have only found the value of one years deposit.

I shall give you 3 points for you honest attempt :)

 Jan 4, 2015

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