Ravina wants to find an estimate for the number of birds in a sanctuary.
She catches a sample of 70 birds in the sanctuary and tags each of these birds.
These birds are then released back into the sanctuary.
The next day she catches a sample of 60 birds in the sanctuary.
Ravina has tagged 12 of these birds.
Work out an estimate for the number of birds in the sanctuary.
Write down an assumption you have made.
