Bhavna has a bag containing a large number of beads.
She wants to find an estimate for the number of beads in the bag.
Bhavna takes a sample of 30 beads from the bag.
She marks each bead with a black cross.
She then puts the beads back in the bag.
Bhavna shakes the bag.
She now takes another sample of 30 beads from the bag.
4 of these beads have been marked with a black cross.
Work out an estimate for the total number of beads in the bag.
Write down any assumptions you have made.
20 exam-style questions on AQA GCSE Maths Capture Recapture. Each one has a worked solution and a mark scheme showing where the marks go.