Çözüldü Algebraic Approach to Percentage Problems

In two successive years, the population of a town has increased by 15% and 20%. What percent of the population has increased after two years?

A) 32%
B) 35%
C) 38%
D) 68%

The initial population of the town: x
x + x·(15 / 100) + [ x + x·(15 / 100) ]·(20 / 100) =
x + 15x / 100 + 20x / 100 + [ x·(15 / 100) ]·(1 / 5) =
x + 35x / 100 + 3x / 100 =
x + 38x / 100 ===> 38%.

Another Solution:
The population has increased by 15% and 20%.
15% increase changes the population to 115% of the original population.
For the second increase, multiply the result by 120%.
(1.15) × (1.20) = 1.38 = 138%
38 percent of the population has increased after two years.

https://www.effortlessmath.com/math-topics/free-parapro-math-practice-test/
(Question 4)