Beth wants to estimate the number of frogs in a lake.
She catches a sample of 80 frogs, marks them and puts them back in the lake.
Later that day, in a second sample of 80 frogs, she finds that some of them are marked.
The estimate for the number of frogs in the lake is 640. Work out how many of the frogs in the second sample are marked.
Write down any assumptions you have made.
87 exam-style questions on Eduqas GCSE Maths Capture Recapture. Each one has a worked solution and a mark scheme showing where the marks go.