The Program in C that prints the sum of 9+99+999+..n terms given below:

```
#include <stdio.h>
int main() {
int n, i, sum = 0;
printf("Enter the value of n: ");
scanf("%d", &n);
for (i = 1; i <= n; i++) {
sum += (i * 111);
}
printf("Sum of %d terms: %d", n, sum);
return 0;
}
```

## Output:

Enter the value of n: 12

Sum of 12 terms: 8658

This program takes an input n from the user and uses a for loop to calculate the sum of the first n terms of the series 9 + 99 + 999 + …

The variable i is used as the current term in the series and is multiplied by 111 to get the next term. The value of i is incremented in each iteration of the loop,

and the sum is stored in the variable “sum”. The final sum is then printed to the console.

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