Multiple choice general knowledge math & puzzles Find the average of first 40 natural numbers ? 40 35 30.6 20.5 Reveal answer Fill a bubble to check yourself D Correct answer Explanation The average of first n natural numbers is (n + 1)/2. For n = 40: (40 + 1)/2 = 41/2 = 20.5. This formula comes from the arithmetic series sum n(n+1)/2 divided by n.