The population of Sundar Nagar in 2001 = Sum of the population of city in 1991 + Increase in population over the given time period
∵ The population of Sundar Nagar in 1991 = 2,35,471
∵ Increase in population over the given time period = 72,958
∴ The population of Sundar Nagar in 2001 = 2,35,471 + 72,958 = 3,08,429