How to print the range of numbers using C language?

In C programming, finding the range of a given number means determining the interval of 10 consecutive numbers within which that number falls. For example, if the number is 45, it falls in the range 40-50.

Syntax

lower = (n/10) * 10;
upper = lower + 10;

How It Works

The logic to find the range uses integer division to extract the tens digit −

• Lower bound: (n/10) * 10 removes the units digit and gives the nearest lower multiple of 10
• Upper bound: lower + 10 gives the next multiple of 10

For example, if n = 45 −

• Lower = (45/10) * 10 = 4 * 10 = 40
• Upper = 40 + 10 = 50
• Range = 40-50

Example 1: Basic Range Finder

Following is the C program for printing the range of numbers −

#include <stdio.h>

int main() {
    int n, lower, upper;
    printf("Enter a number: ");
    scanf("%d", &n);
    
    lower = (n/10) * 10; /* Integer division removes units digit */
    upper = lower + 10;
    
    printf("Range is %d - %d<br>", lower, upper);
    return 0;
}

Enter a number: 25
Range is 20 - 30

Example 2: Range for Larger Numbers

This example demonstrates range calculation for three-digit numbers −

#include <stdio.h>

int main() {
    int number, start, end;
    printf("Enter a number: ");
    scanf("%d", &number);
    
    start = (number/10) * 10; /* Calculate lower bound */
    end = start + 10;         /* Calculate upper bound */
    
    printf("Number %d falls in range %d - %d<br>", number, start, end);
    return 0;
}

Enter a number: 457
Number 457 falls in range 450 - 460

Key Points

• Integer division (n/10) automatically truncates the decimal part
• This method works for positive numbers of any size
• The range always spans exactly 10 consecutive numbers

Conclusion

Finding the range of a number in C uses simple arithmetic operations with integer division. The formula (n/10) * 10 efficiently calculates the lower bound of any number's decade range.