# C++ Program to Calculate Simple Interest

In this post, we will write a C++ program to calculate simple interest. Simple interest is a quick and easy method of calculating the interest charge on a loan. Simple interest is determined by multiplying the daily interest rate by the principal by the number of days that elapse between payments.

The formula for simple interest is given as,

Simple Interest = (principal amount × interest rate × time) / 100

#include<iostream>
using namespace std;
int main()
{
// declare variables
float p, t, r, interest;

// take input from end-user
cout << "Enter principal amount, time and rate:";
cin >> p >> t >> r;

// calculate interest
interest = (p*t*r)/100;

// display result
cout << "Interest = " << interest << endl;

return 0;
}

Output:-

Enter principal amount, time and rate: 1000 10.5 11.9
Interest = 1249.5

Simple interest is calculated as ( principal amount * time * rate ) / 100. So, we need four variables that will store the value of the principal amount, time, rate, and interest. In this C++ program to calculate simple interest, We define four variables p, t, r, and interest which stores principal amount, time, rate, and interest respectively. Using the formula of simple interest, the value of interest is calculated.

## Program to Find Simple Interest Using Function in C++

A function is a block of code that performs a specific task. Every program must have at least one function with the name main. The execution of the program always starts from main function and ends with main function. Main function can call other functions to do some special task.

#include<iostream>
using namespace std;

// function declaration
double calculateInterest(double p, double t, double r);

// main function
int main()
{
// declare variables
double p, t, r, interest;

// take input from end-user
cout << "Enter principal amount, time and rate:";
cin >> p >> t >> r;

// calculate interest
interest = calculateInterest(p, t, r);

// display result
cout << "Interest = " << interest << endl;

return 0;
}

// function to calculate interest value
double calculateInterest(double p, double t, double r)
{
return (p*t*r)/100;
}

Output:-

Enter principal amount, time and rate:10000 5 9.9
Interest = 4950

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