Bingo cards are normally printed in strips of six. A strip of six cards has every number between 1 and 90. Many people buy only 4 cards, so that the other two cards were usually wasted. Edward Thompson and Company, the largest printer of bingo tickets in the UK found a way to print strips of 12 so that there would be less waste, and so that any 6 tickets had all of the numbers 1 to 90.