In this program, you'll learn to calculate the sum of natural numbers using for loop and while loop in Kotlin. You'll also see how ranges can be helpful for solving the problem.

The positive numbers 1, 2, 3... are known as natural numbers and its sum is the result of all numbers starting from 1 to the given number.

For n, the sum of natural numbers is:

1 + 2 + 3 + ... + n

```
fun main(args: Array<String>) {
val num = 100
var sum = 0
for (i in 1..num) {
// sum = sum+i;
sum += i
}
println("Sum = $sum")
}
```

When you run the program, the output will be:

Sum = 5050

The above program loops from 1 to the given `num`(100) and adds all numbers to the variable `sum`.

Unlike Java, in Kotlin, you can use *ranges* (`1..num`

) and *in* operator to loop through numbers between 1 to `num`.

Here's the equivalent Java code: Java Program to Calculate the Sum of Natural Numbers

You can also use while loop to solve this problem as follows:

```
fun main(args: Array<String>) {
val num = 50
var i = 1
var sum = 0
while (i <= num) {
sum += i
i++
}
println("Sum = $sum")
}
```

When you run the program, the output will be:

Sum = 1275

In the above program, unlike a for loop, we have to increment the value of `i` inside the body of the loop.

Though both programs are technically correct, it is better to use for loop in this case. It's because the number of iteration (upto `num`) is known.

Visit this page to learn *how to find the sum of natural number using recursion*.