Example: 1, __ , 3, 4, 5; mean=3
Step 1: Let N be the missing number.
Step 2: We know, Mean = (Sum of all numbers)/(Number of numbers);
Therefore, Sum of all numbers = Mean x Number of numbers
→ 1 + N + 3 + 4 + 5 = 3 x 5 → N + 13 = 15 → N = 15-13 → N = 2