IMAS 2016 — Middle Primary Grades 3–4 — Round 2 Question 12

Six pairs of integers are formed from the list of positive integers 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12. It is known that the sums of the five pairs are: 4, 6, 14, 20 and 21. What is the product of the remaining pair of numbers?