What is the perimeter of a rectangle that has six tiles across and three titles down? Remember to find our perimeter, we add up the number of tiles along each side. Our problem tells us that there are six tiles across and three titles down. Let us double check. One, two, three. We know that there are three tiles down. One, two, three, four, five, six. We know that there are six tiles across. If there are six tiles across this side, we know that there must be six tiles across this side. So, if there are six titles at the bottom, there must be six tiles at the top. If there are three tiles on this side, there must be three tiles on the opposite side. Now, we can make addition in it and add the tiles up. Six plus six plus three plus three is equal to eighteen. The perimeter of this rectangle is eighteen.