Three Ball Line Up

Two children are playing with three balls, one blue, one red and one green.

They toss up the balls, which run down a slope so that they land in a row of three.

In how many different ways could the balls land?
How do you know you have found them all?

You might like to use the interactivity below to explore the problem.
 

If you would like to try another task which involves finding all possible solutions, you could look at Inside Triangles.

You may be interested in the other problems in our Working Systematically Feature.