Liam wants to find an estimate for the number of rabbits in a field.
He catches 30 rabbits from the field and marks each one with a tag.
He then returns the rabbits to the field.
A week later, Liam catches another 45 rabbits.
9 of these rabbits are marked with a tag.
Work out an estimate for the number of rabbits in the field.
Write down an assumption you have made.