 Hi I'm Lucy and in this video we're going to look at how to multiply and divide with surds. We've already looked at how to simplify them in this video and now we're going to learn how to calculate with them. So let's jump straight in with an example. Can you see what's happening? You just multiply the numbers together to make a single surd. Easy! If you know how to simplify surds as we saw in our earlier video we now just work in the other direction. We multiply them together so there's nothing new to learn whatsoever. Why do we do this? We need to sometimes multiply surds together like the root six and root three so that we can then simplify them Root six and root three are as simplified as they can be on their own but root 18 can then be simplified down into root nine root two which is three root two. So that's multiplying surds now for dividing surds. Can you see what's happening? As with multiplying you just divide the numbers. Here are some questions for you to do. Pause the video, work out the answers and click play when you're ready to check. Did you get them right? You may have done different working to what I have but here are some different options. So there we have multiplying and dividing with surds. We often combine these two skills with simplifying at the same time. In the next video we're going to look at when we can and cannot add and subtract surds.