C Exercises: Calculate the simple interest for the loan

Last update on September 18 2025 12:34:58 (UTC/GMT +8 hours)

Compute simple interest

Write a C program that accepts principal amount, rate of interest and days for a loan and calculates the simple interest for the loan, using the following formula.
interest = principal * rate * days / 365;

Sample Input: 10000
.1
365
0

Sample Solution:

C Code:

#include<stdio.h>

int main()
{
    // Declare variables
    float principal_amt, rate_of_interest, days, interest;
    const int yearInDays = 365; // Constant for converting interest rate

    // Prompt user for loan amount
    printf( "Input loan amount (0 to quit): " );
    scanf( "%f", &principal_amt );

    // Main loop for processing loans
    while( (int)principal_amt != 0) 
    {
        // Prompt user for interest rate
        printf( "Input interest rate: " );
        scanf( "%f", &rate_of_interest );
        
        // Prompt user for loan term in days
        printf( "Input term of the loan in days: " );
        scanf( "%f", &days );

        // Calculate interest
        interest = (principal_amt * rate_of_interest * days )/ yearInDays;
        
        // Display interest amount
        printf( "The interest amount is $%.2f\n", interest );

        // Prompt user for next loan principal_amt
        printf( "\n\nInput loan principal_amt (0 to quit): " );
        scanf( "%f", &principal_amt );
    }

    return 0;
}

Sample Output:

Input loan amount (0 to quit): Input interest rate: Input term of the loan in days: The interest amount is $1000.00


Input loan principal_amt (0 to quit):

Flowchart:

C Programming Flowchart: Calculate the simple interest for the loan.

For more Practice: Solve these Related Problems:

Write a C program to compute simple interest for multiple loans stored in an array.
Write a C program to calculate simple interest and then compute the total amount using functions.
Write a C program to compute simple interest and compare it with compound interest for given inputs.
Write a C program to calculate the simple interest for a loan while validating user inputs with error messages.

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