18. Master Li made 8 identical rabbit lanterns in three days, making at least 1 per day. Master Li has ( ) different ways to do this.
【Answer】 21 ways.
【Analysis】Key point: Enumeration method and multiplication principle
Xueersi corresponding lecture: Grade 3 Fall Class Classification and Steps (Lecture 11)
Make 1 lamp each day, and there are still 8-3=5 lamps to be made.
(1) If these 5 lamps are completed in 1 day, there are 3 ways;
(2) If these 5 lamps are completed in 2 days, $5=1+4$ or $5=2+3$;
If 1 lamp is made one day and 4 lamps the next day, there are $3 \times 2=6$ (ways);
If 2 lamps are made one day and 3 lamps the next day, there are $3 \times 2=6$ (ways);
(3) If these 5 lamps are completed in 3 days, $5=1+1+3$ or $5=1+2+2$;
If 3 lamps are made on one day and 1 lamp each on the other two days, there are 3 ways;
If 1 lamp is made on one day and 2 lamps each on the other two days, there are 3 ways; so in total, there are $3+6+6+3+3=21$ (ways).