The football World Cup is back in summer! Do you already have stickers with the football players? And maybe even a scrapbook? Fans have been collecting these player pictures for 50 years. The album for the 2018 World Cup contains 640 pictures. There are five pictures in each of the sachets you can buy. How many bags do you need until the album is full? You can't say exactly: it depends on which pictures are in it and that is a matter of chance. But you can work out pretty well how many sachets you need on average, and how many more or fewer you might need. This can be calculated mathematically - but you can also try it out. And that's exactly what we want to do together in the lecture.

The tricky thing is that with every picture you already have, it becomes more difficult to get one that is still missing from the album. So the last picture is the "most expensive". Why is that? Exciting question - just come to the lecture!