The average income of 5 persons is Rs. 550 and that of another 15 persons is Rs. 450. Find the average income of the whole group.

Average income of 5 persons = Rs. 550

Average income of 15 persons = Rs. 450

​$$\text{Average income} = \frac{\text{Total Income}}{\text{Number of Persons}}$$​​

Total income = Number of persons × Average income

Total income of 5 persons = 5 × 550 = Rs. 2750

Total income of 15 persons = 15 × 450 = Rs. 6750

Total income of the group = 2750 + 6750 = Rs. 9500

Total persons = 5 + 15 = 20

Average income = $$\frac{9500}{20}$$​ = Rs. 475

Thus, the average income of the whole group is Rs. 475.