To find the class mark (xᵢ) for each interval, the following relation is used.
xᵢ = (Upper Limit + Lower Limit)/2
Class size = 50. Taking 225 as assumed mean (a), dᵢ, uᵢ fᵢuᵢ are calculated as follows.

From the table, we obtain
∑fᵢ = 25, ∑fᵢuᵢ = -7, a = 225 and h = 50
mean (X̄) = a + (∑fᵢuᵢ / ∑fᵢ)h = 225 + (-7/25) × 50 = 225 – 14 = 211
Therefore, mean daily expenditure on food is ₹211