1, dividend = quotient.

2. The minimum digit is 1 and the maximum digit is 9; The minimum two digits are 10 and the maximum two digits are 99; The smallest three digits are 100 and the largest three digits are 999; The smallest four digits are 1000 and the largest four digits are 9999; The largest five digits are 10000.

3. When converting length units, large units are converted into small units, and the numbers increase (add "0"), while small units are converted into large units, and the numbers decrease (remove "0").

4. End time-elapsed time = start time.

5. subtraction: calculate first (points MINUS points) and then calculate (hours MINUS points). When the "points" are not reduced enough, the 1 borrowed from (hours) is 60 points, and the 60 points are combined with the original "points" and then reduced.