Sixth grade math problem: bear, rabbit, kitten and puppy stand in a row and form a performance group to sing. Kittens and puppies are required to be adjacent. How many kinds are there? number
Multiplication principle. Think of cats and puppies as a whole, and let bears, rabbits and "kittens and puppies" line up together. One * * is 3x2x 1=6 kinds. Of these six kinds, kittens and puppies may be adjacent to each other, so each kind has two possibilities. One * * is 6x2= 12 station methods.