I designed this worksheet to help pupils to discover Pi, and prove it is not a randomly generated number. It also helps pupil to understand how accuracy can affect results. You will need to provide your pupils with string. The largest circles circumference is 23.56cm. I have used this across both KS3 & KS4, and they have all enjoyed it and found it a good lead into circumference and area of circles. I welcome any feedback on this activity.