 So we heard a course from your tale how it's really important to get the dimensions of a physical quantity, right? If you're talking about energy, it better be a unit of energy. If you're talking about power, it better be a unit of power, and so on. But of course, you also have to actually get the units, right? There's no point specifying something to be 10 meters tall when you actually meant 10 inches tall. And indeed in 1998 the Mars climate orbiter was lost due to a miscommunication in units. They specified thrust in terms of pound seconds instead of Newton seconds. So all they had to do to make that work is to be able to change units. So let's make sure that we can change units. There's a simple trick you can use. So let's take our example of a kilowatt hour again. So a kilowatt times an hour is a unit of energy, and we can turn that into another unit of energy Equals one kilowatt hour times one times one. I can always multiply by one. It doesn't change anything. So I can put anything inside here that adds up to one. So what I'm going to put is I'm going to put I know what a kilowatt is. A kilowatt is a thousand watts. And I've put the kilowatt on the bottom there. So this is one. This is one here because a thousand watts is exactly equal to a kilowatt. That's what a kilowatt means. And then I've put them in that order because that allows me to cancel the kilowatts there. And so now I have a thousand watt hours. But I'm going to go further and I'm going to say well I want to change the hours to seconds. So I'm going to say well I know what one hour is. I'm going to put the hour on the bottom because I want it to cancel with the hour on the top over there. I know that that's equal to 60 minutes. And so we can say that 60,000, and note that the hour is canceled, watt minutes is equal to one kilowatt hour. That's still not a particularly standard unit of energy. So let's keep going. So I've got 60,000 watt minutes. Now what's a watt? A watt is a joule per second. That's how it's defined. And I've got a minute on the top here. So I want to put a minute on the bottom there. So times by one again, I put one minute on the bottom. I put 60 seconds on the top. And what I can see is that my minutes cancel, but also my seconds cancel. And I'm left with 60 times 60,000. And that is now in joules. Or if I wanted to make it simpler, I could note that I've got 3.6 megajoules because a megajoule is a million joules. Okay, so that's a way we can just convert. So the trick there is we just keep on multiplying by one.