How to Find the Perimeter of a Rectangle Math with Mr J

Welcome to Math with Mr. In this video, I'm going to cover how to find the perimeter of rectangle. Now, remember, perimeter is the distance around the outside of shape. Let's jump into our examples, starting with number one. So, let's find the perimeter of this rectangle, and we can do this by adding the lengths of all of the sides. So, perimeter equals, well, we have 13 yd on these two sides, and then 5 yd on these two sides. So, we have 13 + 13 + 5 + 5. And now we can add. 13 + 13 is 26 + 5 is 31 + 5 is 36. So, the perimeter is 36 yd. That's the distance around that rectangle. Now, do want to mention, it doesn't matter what order you add those side lengths in. You'll get the correct perimeter however you do it. So, something to keep in mind. Now, as far as rectangles go, we can also find the perimeter by, let me write this out, perimeter equals, well, multiplying the length by two, and I'm going to use cursive so it doesn't look like one, plus and then multiply the width by two. So, we can use this formula as well, just different way to set it up. Essentially, it's the same thing. You can see that we have two 13s here, and then two fives. So, two times the length plus two times the width. Now, I'm going to use the longer side for the length, 13, and then five for the width. Let's plug these in. So, perimeter equals two times 13 plus two times five. So, now let's work through this. And remember, we always multiply before we add. So, we need to do two times 13 and two times five. So, perimeter equals, well, two times 13 gives us 26 + 2 * 5 gives us 10. Now, we can add. 26 + 10 gives us perimeter of 36 yd. So, we get 36 yd that way as well. So, for the perimeter of rectangle, either way will work. We can either add all of the side lengths, or we can do two times the length plus two times the width. Now, one more thing do want to mention before moving on to number two, if we were to switch the length and the width, for example, use five for the length and 13 for the width, we're still going to get the correct perimeter. And for number one, we're still going to get 36 yd. So, don't get too held up on that. Again, used the longer side for the length. Let's move on to number two and find the perimeter of that rectangle. Now, you'll notice that we are only given two sides. We have 32 cm right here and 9 cm right here. Well, since this is rectangle, we know that the opposite sides are going to be the same length. So, across from 32 cm is going to be 32 cm. Across from 9 cm is going to be 9 cm. also included tick marks to show this. One tick mark right here matches one tick mark right here. That shows that those sides are the same. They are both 32 cm. And then two tick marks right here matches two tick marks right here, showing that those sides are the same. They are both 9 cm. And then also included these symbols to show that these are all right angles, 90° angles. wanted to include all of these symbols in case you come across them. That way, you'll know what they mean. So, something else to keep in mind. Now, as far as the perimeter, let's add all of the side lengths. So, perimeter equals 32 + 32 + 9 + 9. 32 + 32 is 64 + 9 is 73 + 9 is 82. So, we have perimeter of 82 cm. Now, let's also multiply the length by two and the width by two and then add those. So, let's do it that way as well. So, perimeter equals two times the length + 2 * the width. Let's use 32 for the length. So, 2 * 32 plus and then nine for the width. So, 2 * 9. Let's multiply now. 2 * 32 is 64 + 2 * 9 is 18. 64 + 18 gives us perimeter of 82 cm. So, we get the same perimeter that way as well. Now, again, do want to mention, used the longest side for the length in both of these examples. If we do switch up the length and the width, we're still going to get the correct perimeter. So, don't get too held up on which is the length and which is the width. If you want to keep it consistent, just go with the longest side for the length. So, there you have it. There's how to find the perimeter of rectangle. hope that helped. Thanks so much for watching. Until next time. Peace.