give explanation of given 2 lines: sum=sum+(i*rem); i=i*10;

[hamayun]

This is my assignment but I don't know where to start and I need your help... give explanation of given 2 lines sum=sum+(i*rem) ; i=i*10;

[donbock]

It is one thing to explain what two lines do; it is another entirely to explain what they are trying to accomplish. You need more context to understand the intent of these lines.
Do you have more context for these two lines?

[whodgson]

sum=sum+(i*rem); 
i=i*10;

int a=15;
int b=3;
int rem=a/b;//rem=3
int sum=0;
sum=sum+(i*rem);//is same as sum+=i*rem
for(int i=0;i<3;i++){
    i=i*10;//same as i*=10
    cout<<i;//prints 0 10 20}
for(int i=0;i<3;i++){    
    sum+=i*rem;
    cout<<sum;//prints 0 3 9}
}

[donbock]

I'm sorry - I don't understand what this program is trying to do. Can you tell us?

Line 5 of the larger snippet doesn't belong: it uses i before that variable has been declared or initialized.

I would have guessed that the variable name rem was short for remainder, but line 3 assigns the quotient of a/b to rem.

The loop in lines 6-8 has nothing to do with a, b, or rem. It just prints the values of 0*10, 1*10, and 2*10. The point of this escapes me.

Knowing that rem is 3, the loop in lines 9-12 prints the values of 0+(0*3), 0+(0*3)+(1*3), and 0+(0*3)+(1*3)+( 2*3). The point of this escapes me.

[PreethiGowri]

i=i*10

#include<stdio.h>
int main(){
int i=2;
printf("before any operation i = %d",i); // o/p i=2
i=i*10;
printf("after above operation operation i = %d",i);// o/p i=20
}

sum = sum+(i*rem);

#include<stdio.h>
int main(){
int i=2,sum=0,rem,a=6,b=5; 
printf("before any operation i = %d",i);
i=i*10;
printf("after above operation operation i = %d",i);
rem = a%b; //a%b yields reminder
sum = sum +(i*rem); // sum = 0+(20 * 1)
printf("after above operation operation sum = %d",sum);}

[donbock]

This is just a wild guess. Perhaps the intent is to demonstrate how the integer division and multiplication instructions (/ and % and *) work in mathematics as well as in C. I'm not sure how to relate this to the original question.

void divideDemo(int dividend, int division);
int multiplyDemo(int multiplier, int multiplicand);

void divideDemo(int dividend, int divisor) {
   int quotient, remainder, checkValue;
   quotient = dividend / divisor;
   remainder = dividend % divisor;
   printf("divide: %d divided by %d = %d remainder %d\n",
          dividend, divisor, quotient, remainder);
   checkValue = multiplyDemo(quotient,divisor) + remainder;
   printf("divide: ((%d * %d) + %d = %d) == %d\n",
          quotient, divisor, remainder, checkValue, dividend);
   }

int multiplyDemo(int multiplier, int multiplicand)
   int i, polarity, product;
   polarity = 1;
   if (multiplier < 0) {
      polarity = -polarity;
      multiplier = -multiplier;
      }
   if (multiplicand < 0) {
      polarity = -polarity;
      multiplicand = -multiplicand;
      }
   product = 0;
   for(i=0; i<multiplicand, i++)
      product += multiplier;
   if (polarity < 0)
      product = -product;
   printf("multiply: %d * %d = %d\n",
          multiplier, multiplicand, product);
   return product;
   }