## How to find Simple Interest with JavaScript:

Let’s learn how to calculate and print the simple interest in *JavaScript* with examples. The program will take the values as inputs from the user and print the calculated Simple Interest.

### How to calculate Simple Interest:

To calculate the *simple interest*, we need to get the *pricipal amount*, *rate of interest*, and the *time period in years* to calculate the interest. If `P`

, `r`

, and `n`

are the values of the principal amount, rate of interest, and time-period, we can calculate the simple interest by using the below formula:

`Simple Interest = (P * n * r)/100`

We need these three values as inputs from the user and we can calculate the simple interest.

### Method 1: By using predefined values:

In this method, we will use predefined *principal amount*, *interest rate*, and *time period* values. The program will calculate the result with the above formula.

```
const p = 1200;
const n = 5;
const r = 0.2;
const simpleInterest = (p * n * r) / 100;
console.log(`Simple Interest: ${simpleInterest}`);
```

- Download it on Github

Here, we are using predefined values for `p`

, `n`

, and `r`

. The calculated simple interest is assigned to the `simpleInterest`

variable. If you run this program, it will print the calculated simple interest value.

`Simple Interest: 12`

### Method 2: By using user-input values:

The following example will take the values as inputs from the user and print the calculated *simple interest*. Create one file `index.html`

and add the below code to it:

```
<!DOCTYPE html>
<html lang="en">
<head>
<script>
function calculateSI() {
let p = document.getElementById("inputP").value;
let n = document.getElementById("inputN").value;
let r = document.getElementById("inputR").value;
let simpleInterest = (p * n * r) / 100;
document.getElementById("result").innerHTML = simpleInterest;
}
</script>
</head>
<body>
<h4>Enter the principal amount:</h4>
<input id="inputP" />
<h4>Enter the rate of interest:</h4>
<input id="inputR" />
<h4>Enter the time:</h4>
<input id="inputN" />
<br /><br />
<button onclick="calculateSI()">Calculate Simple Interest</button>
<p id="result"></p>
</body>
</html>
```

- Download it on Github

Here,

- We have three input fields to take the
*principal value*,*rate of interest*, and*time*. - There is one button, on clicking this button, it calls the
`calculateSI`

function. This function calculates the simple interest with the user-provided value.- Inside the function, it reads the value of the principal amount, interest rate, and the number of years and assigns these values to three different variables.
- It calculates the simple interest value and assigns it to the
`simpleInterest`

variable. - This value is assigned to the
`p`

component`result`

.

If you open this file in a browser, it will look as below:

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