Computing compound interest question

raneie (10)
Hi everyone! I have a question about computing compound interest.

What I'm trying to do is display all of the years and their total deposit amounts, depending on the number the user inputs for the years. So if the user inputs 5 for the amount of years, I want the output to show years 1 - 5 and their deposit amounts. How would I be able to do that?

Here's my code (Getting the user's inputs are in a separate file, this is where I'm doing the calculation and displaying):

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#include <iostream>
#include <iomanip>

using namespace std;

double Compute_Investment(double principal, double interestRate, int years)
{
	double totalAmount;

	totalAmount = principal * pow((1 + interestRate/100), years);

	cout << endl;

	cout << "Years" << setw(25) << "Amount of Deposit" << endl;
	cout << setprecision(2) << fixed;
	cout << setw(4) << "1" << setw(10) << totalAmount;




	return totalAmount;
}


I want the output to look like this:


Year Amount of Deposit
1        $1050.00
2        $1102.50
3        $1157.63
4        $1215.51
5        $1276.28
Last edited on
lastchance (6980)
Use a loop.
raneie (10)
How would that look like in the code?

Sorry I'm a newbie :PP
lastchance (6980)
raneie (10)
I got the loop to work, now I have one more tiny problem:

How would I make it so that the lowest calculation goes first?
Also, how would I make the year increase?

How it looks now:

Year Amount of Deposit
1        $1276.28
1        $1215.51
1        $1157.63
1        $1102.50
1        $1050.00


How I want it to look:

Year Amount of Deposit
1        $1050.00
2        $1102.50
3        $1157.63
4        $1215.51
5        $1276.28
lastchance (6980)
You haven't shown your loop - difficult to comment on what we can't see!
raneie (10)
Sorry my bad LOL

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#include <iostream>
#include <iomanip>

using namespace std;

double Compute_Investment(double principal, double interestRate, int years)
{
	double totalAmount;

	for (int years1 = years; years1 > 0; years1--)
	{
		totalAmount = principal * pow((1 + interestRate / 100), years1);

		cout << endl;

		cout << "Years" << setw(25) << "Amount of Deposit" << endl;
		cout << setprecision(2) << fixed;
		cout << setw(4) << "1" << setw(10) << totalAmount;

	}

	cout << endl;




	return totalAmount;
}
lastchance (6980)
(1) If you want the years to go forward ... then start with 1 and count UP, not down!

(2) DON'T use pow(). Simply set totalAmount=principal before the loop and multiply totalAmount by ( 1 + interestRate / 100) once on each pass through the loop. After all, that's what the bank does!

(3) If you want to output the year then output the loop index, NOT 1, every time.

(4) Choose a counter-type name, like i or n, for the loop index, not year1, which is rather close to an existing variable.
raneie (10)
When I try to count up, it starts at what the user inputs.
So for example if the user inputs 5, it will start from 5 and count up. Not only that, but it will increase infinitely

Here's my code:
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#include <iostream>
#include <iomanip>

using namespace std;

double Compute_Investment(double principal, double interestRate, int years)
{
	for (int n = 1, i = years; n = i; n++, i++) //CHANGED HERE
	{
		double totalAmount;
		totalAmount = principal * pow((1 + interestRate / 100), n);

		cout << endl;

		cout << "Years" << setw(25) << "Amount of Deposit" << endl;
		cout << setprecision(2) << fixed;
		cout << setw(4) << n << setw(10) << totalAmount;

	}

	cout << endl;




	return 0;
}


The output:

Years        Amount of Deposit
   5   1276.28
Years        Amount of Deposit
   6   1340.10
Years        Amount of Deposit
   7   1407.10
Years        Amount of Deposit
   8   1477.46
Years        Amount of Deposit
   9   1551.33
Years        Amount of Deposit
  10   1628.89
Years        Amount of Deposit
  11   1710.34
Years        Amount of Deposit
  12   1795.86
Years        Amount of Deposit
  13   1885.65
Years        Amount of Deposit
  14   1979.93
Years        Amount of Deposit
  15   2078.93
Years        Amount of Deposit
  16   2182.87

etc...
lastchance (6980)
Initialise totalAmount to the principal before the loop.

Don't use pow(). Read my previous post.

I've no idea why you have BOTH n and i, or how they got so confused. Start with n=1 and loop while n<= years. If n is your loop index then i isn't needed.

Are you sure that you're not yet another incarnation of Rascake?
raneie (10)
idk who or what Rascake is LOL (maybe i am??? idk)
I just signed up today because I was struggling :PP

Anyways, I got the program to work so it's all good

Thanks for your help!
Last edited on
mbozzi (3932)
Rascake was the username of one particularly long-lived troll account. If you're curious.
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