Chapter 3 – #18: Interest Earned – Tony Gaddis – Starting Out With C++

>_ Problem

Assuming there are no deposits other than the original investment, the balance in a savings account after one year may be calculated as

Amount = Principal * (1 + Rate / T) ^ T

Principal is the balance in the savings account, Rate is the interest rate, and T is the number of times the interest is compounded during a year (T is 4 if the interest is compounded quarterly).
Write a program that asks for the principal, the interest rate, and the number of times the interest is compounded. It should display a report similar to

Interest Rate:                                  4.25%
Times Compounded:                       12
Principal:                           $    1000.00
Interest:                             $          43.34
Amount in Savings:     $     1043.34

>_ Solution

#include <iostream>
#include <iomanip>
#include <cmath> 
using namespace std;

int main()
{
    // Constant
    const int ONE     = 1,
              HUNDRED = 100;

    // Variables
    float principal,                // Principal
          interest_rate,
          amount_after_a_year,      // Amount
          total_interest,
          amount_in_savings;

    int times_interest_compounded;  // T

    // asks for the principal, interest rate, and number of times the interest is compounded
    cout << endl;
    cout << "What is the pricipal balance in the" << endl;
    cout << "savings account? ";
    cin >> principal;

    cout << "What is the interest rate? %";
    cin >> interest_rate;

    cout << "What is the number of times the interest\n";
    cout << "is compounded during a year? ";
    cin >> times_interest_compounded;

    // Calculate
    interest_rate /= HUNDRED; // 4.25% == .0425
    // Amount = Principal * (1 + Rate/T)^T
    amount_after_a_year = principal * pow((ONE + interest_rate/times_interest_compounded), times_interest_compounded);

    total_interest = amount_after_a_year - principal;

    interest_rate *= HUNDRED;

    // Display
    cout << setprecision(2) << fixed << right << endl;

    cout << "Interest Rate:        " << setw(10);
    cout << interest_rate << '%' << endl;

    cout << "Times Compounded:     " << setw(10);
    cout << times_interest_compounded << endl;

    cout << "Principal:           $" << setw(10);
    cout << principal << endl;

    cout << "Interest:            $" << setw(10);
    cout << total_interest << endl;

    cout << "Amount after a year: $" << setw(10);
    cout << amount_after_a_year << endl;

    // Terminate Program
    return 0;
}

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>_ Video Walk Through

This video includes a step by step process of how I solve programming challenge #18.

>_That’s it!

Thank you for taking interest what I do! I hope it was helpful for you as much as it helped me along my journey in learning to code!

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Category: Starting Out With C++ | Chapter 3 | Programming Challenge Solutions

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