Three children are sharing a bike and a skateboard. How many different groups of 2 children can ride these toys at one time?
So, this question is asking you for the number of different groups of children who can ride some toys at one time.
- How many total children are there? Just so we can follow along, let's call that number "N"
- How many children can ride the toys at one time? That is, how many toys are there? Let's call that "R"
The question is now, how many different groups of R children can be formed from a total of N children?
Depending on what level of math you're in, those groups of children have a special name. They're either permutations or combinations. If those words mean something to you, then the question is: which one are we talking about here?
If you're not at that level yet, and you have no idea what a combination or a permutation is, then this is a different question. :) How about picking names for the N children and seeing how many different ways you can pick R of them? There aren't too many, so you might be able to count them by hand...
Hope some of this helps,