First I really discuss the difference between the area and perimeter. I always say that you need to know the area to put carpet or tile in room, and perimeter is like a fence to keep your dog in. When I am teaching how to find a missing side when given the perimeter, I tell them to think of the perimeter as pieces of wood for a fence. For examples, if the perimeter is 20 feet and the length is 7 feet, its like the have 20 pieces of wood and 7 of them are on the lengths of the rectangle. I ask the students to tell me how many pieces of wood are left. They know that if the length of the rectangle is 7 then his congruent side has to be 7 too, and when you had those two together you get 14, so they've used 14 pieces of wood. Then I ask the students to tell me how much wood is left, the know that they are to subtract to do this so...20-14 is 6. I have to explain many times that 6 is not the width! If 6 was the width then there would not be enough "wood" left over to close the fence and your dog would run out! So in order to enclose the fence all the way around you have to divide the 6 by 2 since you have two missing sides, and you'd get 3! Length is 7 feet and width is 3 feet, which makes a perimeter of 20 feet! I find that my students will say out loud a lot, "Have to divide by two otherwise the dog will run out!" It is the cutest thing to see that they use what I say and that they grasp what we are doing when trying to find the missing side!

Finding the missing side when given the area my students find pretty easy, they just to the inverse operation. A=LxW so if they are given the area, just divide by the side that is given!

I found a game on pinterest to practice area and perimeter!! The students found a partner and I gave them grid paper and two dice. They rolled the dice and drew the dimensions on the grid paper with a crayon, each pair should each have a different color crayon. The first 10 minutes of the game I had them find the area of the figure they drew and write it in the middle of the rectangle. The second 10 minutes I had them find the perimeter of the figure and write it on the page. They drew their figures on the grid paper and the point of the "game" was to see who could fill up the grid paper the most with their color of rectangles. It was a quick and fun game to practice the skill!

## No comments:

## Post a Comment