Loops doesn't work correctly!!

[BaresiXD]

Hey guys, im new to the C language and i have a problem with loops.
I need to calculate the cost of buying carpets to n houses, every house consists of n rooms, and every room consists of different length and width.

for this i made a loop:

while (i <= rn)
	{
		printf("please enter the lenght of room number %d:",i);
		scanf("%f",&l);
		printf("please enter the width of room number %d:",i);
		scanf("%f",&w);
		printf("please enter the color of room number %d:",i);
		fflush(stdin);
		scanf("%c",&c);
		/*in the second run of the loop, it doesn't allow users to type, it steps over the scanf statments*/
..
..
..
..

what's the problem and every loop in this program steps over scanfs in the second run :S

what to do guys, It's a homework :S

thank u in advance ;)