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CCSS.Math:

what is the perimeter of the shape each square in the grid is a one by one centimeter square so all we have to do is add up the lengths of these blue segments right over here and they put it on this nice grid and each box here is one by one so we could let's say we start up here we want to make sure that we only go to where we started and we don't double count so we this perimeter is 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 centimeters long so it is 24 centimeters the other way we could have thought about this is you could have looked at the length of each of these sides so this is one plus two plus three plus one plus three plus one plus which is five plus two plus four plus two and you would have also gotten 24 centimeters let's do a couple more of these what is the perimeter of the square so once again it's the length of all of the segments that define the outside boundary of the square and by definition 2 square all of its sides are equal so you have four sides that are all 7 meters long so you could say 7 meters plus 7 meters plus 7 meters plus 7 meters or it's 4 times 7 meters or 28 meters 28 meters let's do one more what is the perimeter of the regular pentagon so it's a regular pentagon which means all of its sides have the same length and they give us a side of 1 the length of 1 is 2 so all the sides have length 2 so it's going to be 2 plus 2 plus 2 plus 2 plus 2 or essentially 5 2's or another way of thinking about is it's 5 times 2 which is going to be which is going to be 10 you have five sides of this Pentagon each of those sides are two units long so 2 units long times five sides is going to be 10 units