This is a speaking activity for young learners to practise numbers up to 20 - there are lots of cards as I have really big classes now. You give each learner one card and appoint the one who starts. Then they say out loud what they have and who they are looking for until all of them are formed in a chain/line. They really like this activity. Afterwards you might like to give each learner to do a certain TPR activity with the number they have (for example: jump 4 times, sit down 6 times, bend your knees 3 times and so on).