Arrangement law of interval phenomena
In a closed arrangement, the number of objects equals the number of intervals. Similar phenomena include sawing wood and climbing stairs. There is an 800-meter-long expressway. How many seedlings does it take to plant a poplar tree every 20 meters from beginning to end on one side of the expressway?
The law in simple collocation phenomenon
Such as: clothing collocation, diet collocation, route collocation. There are three roads from Xiaoming's home to Children's Palace, and four roads from Children's Palace to Xinhua Bookstore. How many walking routes are there from Xiaoming's home to Xinhua Bookstore?
Laws in simple periodic phenomena
Example: Xiaohong wrote "Beijing Olympic Games-Beijing Olympic Games-"in turn while practicing hard-pen calligraphy at home. What should the 24th word be?