A certain businessman, who is always in a hurry, walks up an ongoing escalator at the rate of one step per second. Twenty steps bring him to the top. Next day he goes up at two steps per second, reaching the top in 32 steps. How many steps are there in the escalator?
Fundamental Principle of Counting
If event E1 can have n1 different outcomes, event E2 can have n2 different outcomes, ..., and event Em can have nm different outcomes, then it follows that the number of possible outcomes in which composite events E1, E2, ..., Em can have is