Oscar wants to find an estimate for the number of rabbits in a field.
He catches 30 rabbits and fits each rabbit with a small ear tag. He then releases the rabbits back into the field.
Later that day, he catches a second sample of 45 rabbits.
Oscar finds that 10 of these rabbits are wearing ear tags.
Work out an estimate for the number of rabbits in the field.
Write down an assumption you have made.