Arithmetic Grade Five

Lesson One hundred and Fifty-six: More Perimeter and Area

Take a look at the figure on the left. It is not a simple rectangle. Finding the perimeter and area of this shape is a little more difficult than finding the area of a simple rectangle. The first thing you have to do in order to solve these problems is to find the length of the missing sides. If you know the length of the long side and one of the short sides, then you can figure out the length of the other short side by subtracting the length of the known short side from the long side as in: long_side - short_side_1 = short_side_2 You will have to do this for the width sides and the height sides. Using the example we have: missing height= 10 - 6 = 4 missing width= 14 - 4 = 10 Once you have all this information you simply add up all the sides to find the perimeter. 10 + 4 + 6 + 14 + 4 + 10 = 48 units

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