During the first year, the population of a city increased by 5% and during the second year, it diminished by 4%. At the end of the second year, its population was 30,240. The population at the end of the first year was:

Correct option is C

Given:

Population increased by 5% in the 1st year

Then decreased by 4% in the 2nd year

Population at end of 2nd year = 30,240

Find population at end of 1st year

Solution:
Let the population at the end of the 1st year be x
Since population decreased by 4% in 2nd year:

Second year population = $$x \cdot (1 - \frac{4}{100}) = x \cdot 0.96$$​​

​$$x \times 0.96 = 30,240$$​​

​$$x = \frac{30,240}{0.96} = 31,500$$​​

Population at the end of the first year = 31,500. 

Alternate Solution: