Rectangles that have the same perimeter

0:00- [Instructor] We are asked, "Which rectangles have the same perimeter? Choose all answers that apply." So why don't you pause this video and try this before we do this together. Okay, so let's just remind ourselves what perimeter even is. It's the distance going around the outside of a figure like these.

0:19So we just have to figure out the distance going around the outside. We could just count the distance 'cause they have all these units already marked off or we could just measure them and add the lengths of each of the four sides because these are all rectangles.

0:33So in this top one, let's see, this top is one, two, three, four, five, six, seven, eight, nine units long, or wide I could say. And so that means it's also going to be nine units down here. And then how tall is it? One, two, three, four units. So this is four units, and so this would also be four units.

0:56And so the perimeter is going to be 9 plus 4. Let me do that. So it's going to be. Or I could do 9 plus 9, 9 plus 9, plus 4, plus 4, plus 4, plus 4. And that is going to be equal to, let's see, this is 18 plus 16, sorry, not 16, 18 plus 8. What's my brain doing? 18 plus 8 is going to be 26.

1:21And these are just units. They're not telling us that they're meters, or centimeters, or anything like that, so I'll just say units. That's the perimeter of this first figure. Now let's look at this figure over here, and let like ignore that, that might distract us.

1:33Alright, so let's see. We have one, two, three, four, five, six, seven, eight, nine, 10. A width of 10, so that means down here is also going to be 10. And then it's height is two. That's two, and so this is two as well. So its perimeter is gonna be 2 plus 2, 2 plus 2, plus 10, plus 10, plus 10, plus 10.

2:0110 plus 10 is 20, 2 plus 2 is 4, so this is going to be 24 units. So these definitely don't have the same perimeter. Let's look at this last one here. So in this last one, if I were to look at the width, it's one, two, three, four, five, six, seven. So that's seven units, so down here is going to be seven units as well.

2:23And if I were to look at this height, one, two, three, four, five, six. So that's six, and so this is going to be six as well. So the perimeter is this length plus this length, 6 plus 6, plus that length up there, plus 7, plus this length down here. I could have changed the order.

2:45I could have gone 7 plus six, plus 7, plus 6 just to get where I started, but that's the same thing as this. and so this is the same thing as 12 plus 14. 12 plus 14, which is equal to 26 units. So the ones that have the same perimeter are the first one and the last one.