 Here we have three farmers, Bob, Jack and Jill. They need to fence their fields to stop their sheep from running away. However, they're not too sure how much fencing to buy, especially since their fields have different shapes. In order to determine the length of fencing that they need, we're going to use a concept called the perimeter. The perimeter is the distance around the outside of a 2D shape. So what's the perimeter of each farmer's field? We need to work out the distance around the outside of each field. So let's start by finding the perimeter of Bob's simple rectangular farm. Choose a starting point. So I'm going to start in this corner and start adding up the sides 80 meters, add 200 meters, add 80 meters, add 200 meters, which added together gives a perimeter of 560 meters. Can you work out the perimeter of Jack's compound shape? There are 10 sides, so be careful not to accidentally miss one out. Pause the video and give it a go. Did you get 360 meters for Jack's field perimeter? So the final field fence we need to work out is for Jill. Jill's farm is different. For the perimeter, we still need to measure the length around it, but circles only have one side. Do you remember that the perimeter of circles is known as the circumference? So do you remember the equation we used to find the circumference of a circle? 2 pi radius or pi diameter, whichever one you prefer. Pause the video and work out the circumference of Jill's field to find the perimeter. Did you get 628 meters for the amount of fence Jill needs? So now the three farmers know how much fence to buy. Sometimes more complicated perimeters may require you to use both the circumference of a circle and general side lengths. Here's an example to finish up. Can you find the perimeter of these compound shapes? Pause the video and give them a go. Did you get 32.9 meters and 64 meters? Let's quickly have a look at where these numbers came from. Split the shape up into a rectangle and a semicircle. For the rectangle, we only want these three sides and then we only want the circumference of half the circle, hence divide by two. Add the perimeters together and we get 32.9 meters. The other shape needs a little less work. Simply work out the missing dimensions of 7 meters and 8 meters and then add them up as you normally would. So from this video you should know that the perimeter is the distance around the outside of a 2D shape and you've practiced finding the perimeter for simple shapes, compound shapes and even circles. See you soon. Please like and share our videos with your friends. If you have any questions that you want to help with, just comment below.