Afamily of four want to go to cat island. but their boat only can fit two individuals if they are both children. how do all four people get to the island in the smallest amount of trips?

The boat can fit two children at one time but not two  adults. Then we have the issue of it not specifying if they are all adults or two adults and two children or 1 adult with three children.  so solution have a child and adult go together. with a child in the adults lap. while it is not safe it is possible (warning this is a answer that could irritate any teacher with sense) or presuming this is a family of two adults ad two children, send the two children first together then send the adults separate 3 trips in total 

Im not sure but maybe 1 adult and one child but im not sure if this is a trick question

These are the multiples of 15 but what you are probably asking or what are the factors of 15