C programming help for beginning C class?

I'm having trouble with the equations needed. we have learned the loops so far and i think this problem wants me to use the loops, and it looks like i need if-else as well. Here is the problem.





Write a program that asks the user to supply three positive integers k, m and n, with k being greater than 1. the program should compute the sum of all the integers between m and n that are divisible by k.





I don't know how to tell C that that i only want an integer evenly divisible by another. and then, i'm not quite sure how to get the addition of those integers done.

C programming help for beginning C class?
int sum = 0;


for (int i=m; i%26lt;=n; i++)


if ((i % k) == 0) sum += i;





Use the "modulus" operator ("%"). It's the remainder of the first number, when divided by the second. When this is zero, the first number evenly divides by the second one.





So, for example,


5 % 3 = 2,


6 % 3 = 0,


7 % 3 = 1





And if you don't want to include m or n in the list, change the loop from:


for (int i=m; i%26lt;=n; i++)


... to:


for (int i=m+1; i%26lt;n; i++)





And make sure m is the smaller of the two numbers. You can swap them if not.





=====================


As an alternative, you don't have to check every single number. You could write:


for (int i=(n-(n%k)); i%26lt;=m; i+=k)


if (i %26gt;=n) sum += i;





... which starts i off as the biggest multiple of k less than or equal to n, and increments i by k in each loop iteration.





You can get rid of the if statement if you initialize i a little better:


for (int i=((n-1+k)-((n-1)%k)); i%26lt;=m; i+=k) sum += i;
Reply:You must ensure that the loop terminates (so that it doesn't last forever). This is how:





#include %26lt;iostream.h%26gt;





void main()


{


int m,n,k , i ,sum = 0;





cout %26lt;%26lt; "Enter k: ";


cin %26gt;%26gt; k;


if( k %26lt;= 1)


cout %26lt;%26lt; "k must be greater than 1";


else


{


cout %26lt;%26lt; "Enter m: ";


cin %26gt;%26gt; m;


cout %26lt;%26lt; "Enter n: ";


cin %26gt;%26gt; n;


if(m %26gt; n)


{


m = m + n;


n = m - n;


m = m - n;


}


for(i=m ; i%26lt; n; i++)


{


if(i % k == 0)


sum +=i;


}


cout %26lt;%26lt; "Sum is " %26lt;%26lt; sum;


}


}





You have to check if m%26gt;n otherwise the loop





if(i = m; i%26lt; n; i++)





will never terminate.


We do this by swapping m and n if m%26gt;n


This is the classic way of swapping 2 numbers with only 2 variables:





m = m + n;


n = m - n;


m = m - n;





This is a complete program - compile and run this to see for yourself.
Reply:if (i % k)


{ i is evenly divided by k }


else


{ there is a remainder after the divide }