This is the solution to the monthly maths problem from RTSdécouverte - Crossing a river
There are a number of possible solutions. Here is one involving nine crossings of the river.
The son and daughter cross over.
The son goes back alone.
The mother then crosses with the dog.
The girl returns alone.
The son and daughter cross together (again).
The son goes back alone (again).
The father then crosses over alone.
The girl takes the boat back.
Finally, the son and daughter cross for a final time.
You can read the original problem here: Crossing a river