Because if one car is going 60 and the other car is going 60, then the average must be 60. Well, if you use the formula to find the average from a mathematics point of view, you will see that it's 60 plus -60, gives you zero divided by two, which is zero. So sometimes from a mathematics point of view, taking the average in the same way that you did here doesn't make sense. Because in the real world, if you have two cars traveling at some speed and you take their average, how can the average be zero? So that's where the root mean square formula comes from. What this formula does is it takes away these negatives and gives you the value of this type of average without the negatives.