Two cars, A and B, are driving in opposite directions at the same time. They met for the first time at a distance of 60 kilometers, and returned immediately after arriving at each other's starting point. On the way, they met again at a distance of 40 kilometers. How many kilometers is there between A and B?

Analysis: When we first met, the two cars walked the whole journey together. At this time, A walked 60 kilometers.

When they met for the second time, the two cars walked three full distances, and A should have walked 60× 3 =180km. At this time, A is 40 kilometers away from A, and with these 40 kilometers, A has just walked two whole journeys, so one whole journey should be: (180+40) ÷ 2 = 168.

This kind of problem, even if it is difficult to make equations, the key is to find out the distance relationship, and you can't do it without understanding the thinking.