Multiply a given number by 3.5 without using the multiplication operator (*)

#include<stdio.h>

int main()

{

    int num;

    int result;

    printf("Enter the number: ");

    scanf("%d",&num);

    result = ((num << 2) - (num >> 1));

    printf("\nResult = %d",result);

    return 0;

}

Explanation

Lets take the input as 10

10 = 0x1010 in hex

So,

                            0x1010 << 2 = 0x101000 = 40

                            0x1010 >>1 = 0x0101  = 5

hence 

                            result = 40 - 5 =35 = 10*3.5

You can try with other numbers as well.