The term “cogent” refers to an argument or case that is clear, logical, and convincing. In the context of the sentence, describing the reasoning as “cogent” suggests it is so well-presented and convincing that it should be obvious to anyone, making it difficult to understand how it could deceive.
Arun’s present age in years is 40% of Barun’s. In another few years, Arun’s age will be half of Barun’s. By what percentage will Barun’s age increase during this period?