Hi everyone and welcome to this video. Today I'm going to explain to you how to calculate a gradient. Now, before you do something like that, it's always very important to know what you are doing because that would make it easier to remember. Now, the gradient is basically how steep a slope is between two different places. Now, that is the simplest way of explaining it. So, the formula is gradient equals vertical interval over horizontal equivalent. Now, what does this tell you? It tells you the vertical interval is the difference in height between those two locations on the map. So, it's a simple calculation: 200 minus 140 or something like that. And the horizontal equivalent is simply the distance between those two places. So, you are going to calculate if you have 25 centimeters on your map, then you are going to calculate the real distance between those two places. So, let's have a look at our map. Here we have a few contour lines. Now, it's important to understand what they represent. A contour line is a line that connects every place with the same altitude. So, in other words, on this line here, for example, each and every place on the line, it doesn't matter where we go, it could be here, it could be there, or yet, every single place on this line is 1020 meters above sea level, right? So, your teacher might ask you to calculate the gradient between point A and point B. Now, the first thing you need to know is what is the height of point A. So, there are no numbers on this side of the map, but if you just trace this line, if you go all along this line, you'll see that it's 1020 because every place on this...