Swami's father has presented him with a word problem about two popular avatars of the Hindu god, Vishnu: Rama, who is known for his purity, and Krishna, who is known for his compassion and tenderness. Swami's father is really only concerned with whether or not his son can do the math problem presented by the textbook, but Swami himself is concerned with whether or not the mangoes are ripe and with whether or not the price of fifteen annas is appropriate for these ten mangoes. If the mangoes are unripe, Swami feels, then the price Rama sets is too high.
Furthermore, since Rama is associated with purity and fidelity, it would seem to go against his character to try to cheat Krishna. On the other hand, he thinks, it is impossible for Swami to know what the "fool Krishna" might pay for four mangoes. It is telling, I think, that the avatar associated with compassion is thought of as a "fool" by Swami, a young boy.
Swami is concerned about what is fair, even perhaps considering what he knows to be true of the Hindu deities, rather than the simple math problem. His father, however, berates him for not just answering the question. In other words, then, Swami clearly values justice and empathy, and he considers what he knows about the characters in the story before he is willing to make an answer. His father, however, does not value these qualities—he just wants the math problem solved—and it seems even that Swami has been taught that Krishna, with his tenderness and love, is foolish and could, perhaps, be taken advantage of.
Swami, then, is innocent and thoughtful, unwilling to reduce an interaction so seemingly complex to something as simple as a problem requiring division and addition. I'm not sure he is terribly unusual, though. Children are often like this—imaginative and questioning, thoughtful and, at times, frustrating—and often adults just want the answer. Most adults are far less imaginative and thoughtful than children are. Children are often encouraged to grow up and be more "logical" or less emotional, and so they learn to be adults through processes and interactions like the one Swami has with his father.