C# Program to Calculate Simple Interest

Simple Interest is the interest calculated only on the initial principal amount taken. This is not like compound interest where interest is compounded, i.e., previous interest is included in the current time period. This interest is simple and grows linearly over time.

In this article, we will discuss how to calculate simple interest using C#.

The formula to calculate Simple Interest is:

Simple Interest (SI) = P × R × T / 100

Where:

• p is the principal amount
• r is the interest rate
• t is the time period in years

Example

Input:
principal = 10,000
rate = 10
years = 2

Output:
Simple Interest = 2000

Input:
principal = 3,000
rate = 5
years = 2

Output:
Simple Interest = 300

Calculating Simple Interest Using Direct Formula

We first take principal as p, rate as r, and time period as t. Now we use the formula for calculating simple interest. After calculating, we return the result. The formula for Simple Interest is:

Simple Interest = P × R × T / 100

Steps for Implementation

• We take input for principal, rate, and time.
• Apply the formula for calculating simple interest: SI = P × R × T / 100.
• Return the calculated simple interest.

Implementation Code

using System;

class Program
{
    static void Main(string[] args)
    {
        // Take the Principal amount
        double principal = 10000;

        // Annual rate of interest
        double rate = 5;

        // Time in years
        double time = 2;

        // Calculate the Simple Interest
        double simple_Interest = (principal * rate * time) / 100;

        // Output
        Console.WriteLine("The Simple Interest is: {0}", simple_Interest);
    }
}

Output:

The Simple Interest is: 1000

Time Complexity: O(1), constant time

Space Complexity: O(1), constant space

Calculating Simple Interest Using Iterative Approach

We can use an iterative approach to calculate simple interest. This involves manually adding the interest for each year in a loop. After the loop completes, we return the total simple interest.

Steps for Implementation

• We first take input as principal, rate, and time period.
• Use a loop to calculate the interest year by year and add the interest for each year.
• Return the total simple interest.

Implementation Code

using System;

class Program
{
    static void Main(string[] args)
    {
        // Input values
        double principal = 10000;
        double rate = 5;
        double time = 2;

        // Calculate simple interest using loop
        double total_Interest = 0;
        for (int i = 0; i < time; i++)
        {
            total_Interest += (principal * rate) / 100;
        }

        // Output the result
        Console.WriteLine($"The Simple Interest is: {total_Interest}");
    }
}

Output:

The Simple Interest is: 1000

Time Complexity: O(n), as we are using a loop to traverse for each year

Space Complexity: O(1), constant space