Concept:The series follows a pattern where each term increases by multiples of 5.Explanation:Find the differences between consecutive terms: 11 - 6 = 5, 21 - 11 = 10, 36 - 21 = 15, 56 - 36 = 20. The differences increase by 5 each time. The next difference should be 20 + 5 = 25. Add 25 to the last term: 56 + 25 = 81.
