Hi, in this session we will be doing the concept of Proportionality of Speed and also Average Speed. What really is speed, well, a vehicle which covers a certain distance in certain amount of time, well, it would have covered this distance in some time, it would have travelled in some speed. So speed is nothing but distance upon time. As you would have seen from the formation, speed and distance would be directly proportionate, which means at a higher speed you are expected to cover longer distance in the same amount of time, right. On the other hand, speed and time as you can see are inversely proportionate, which means to cover the same distance you will take less time at a higher speed. Well, that is the proportionality of speed, time and distance. What that means is, if the speed changes in the ratio a is to b, then the time taken to cover the same distance, since time and speed are inversely proportionate, time taken would be in the ratio b is to a, while the distance covered in the same amount of time, remember distance and speed were directly proportionate, so distance covered would be in the same ratio which is a is to b. Let us now look at some of the conversions. How do you convert speeds from meter per second to kilo meters per hour. So one kilo meter per hour is nothing but 5 by 18 meters per second. Which means if I have to convert any value of speed from kilometre per hour to meters per second, I multiple 5 by 18. One meter per second on the other hand would be 18 by 5 kilo meter per hour. It is the reverse, Any idea what is 1 mile, well 1 mile is 1.6 kilo meters so 1 mile per hour would be nothing but 1.6 kilo meter per hour. Now that is as far as the proportionality of Speed, Time and Distance is concerned. Let’s look at the next topic which is Concept of Average Speed. Now when do we use this concept of average speed. When a vehicle is covering different speeds for different amount of time or different distances at different speeds, for example, when different parts of the journey is covered at different speeds, concept of Average Speed comes into play. So let’s look into this particular train.