Question 24
Each of 1, 2, 3, 4, 5, 6, 7, 8 and 9 is written on one card. A takes away two cards whose numbers have sum 14. B takes two cards whose numbers differ by 6. C takes away two cards with numbers whose numbers have product 12. D takes away two cards such that the number on one of them is twice the number on the other. What number is on the card not taken away?