There are 20 people in a room. Each person shakes each other person's hand once.
Work out the number handshakes that take place.
Practise OCR GCSE Maths The Product Rule for Counting with exam-style questions for Foundation and Higher tier. 68 questions, matched to the OCR GCSE Maths (J560) specification and written in the written papers style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.