In a modern elevator system which there are @ 4 to 6 cars and a single external keypad for selection of the desired floor, what is the mathematical formula used for the selection of a particular elevator car to be used for the inputted floor. Basically, how is a car chosen to be programmed to go to a selected floor out of the other elevators to choose from?

 

Not a math formula, but an algorithm. Algorithms will vary by system of course.

One which was explained to me, running in one of our downtown high-rise buildings: Each car gets points for answering a call. The car closest to a call floor will answer the call IF it is going in the convenient direction and IF it is not at capacity. If two or more cars tie, the car with the least points will answer the call.