The arithmetic mean of the following numbers : 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6 and 7, 7, 7, 7, 7, 7, 7 is -

According to the question,
Average = $$\frac{1 + 2 + 2 + 3 + 3 + 3 + 4 + 4 + 4 + 4 + 5 + 5 + 5 + 5 + 5 + 6 + 6 + 6 + 6 + 6 + 6 + 7 + 7 + 7 + 7 + 7 + 7 + 7}{28}$$
Average = $$\frac{1 + 2 × 2 + 3 × 3 + 4 × 4 + 5 × 5 + 6 × 6 + 7 × 7}{28}$$
Average = $$\frac{1 + 4 + 9 + 16 + 25 + 36 + 49}{28}$$
Average = 5