Pointing to a photograph, a man said, "I have no brother or sister, but that man's father is my father's son." Whose photograph was it?

Introduction / Context:

This is a classic blood-relation puzzle often seen in aptitude tests. The speaker highlights that he has no siblings and then relates the man in the photograph to "my father's son". Carefully understanding who "my father's son" is when there are no brothers or sisters is the key to identifying whose photograph it is.

Given Data / Assumptions:

• The speaker is a man.
• He says: "I have no brother or sister."
• He also says: "That man's father is my father's son."
• We must identify the relation of the man in the photograph to the speaker.
• We assume a simple family: the speaker's father has only one son (the speaker).

Concept / Approach:

The crucial expression is "my father's son". Because the speaker has no brother or sister, the only son of his father is the speaker himself. Once we substitute this back into the sentence, we get a direct relationship between the man in the photograph and the speaker: the man's father is the speaker, so the man must be his son. Finally, we phrase the answer as "his son's photograph".

Step-by-Step Solution:

Verification / Alternative check:

Let F be the speaker's father and S be the speaker. Since S has no siblings, F's only son is S. Let X be the man in the photograph. The statement says that X's father is F's son, which is S. So X is a child of S, making X his son. This matches the previous reasoning and confirms that the photograph is of his son.

Why Other Options Are Wrong:

It cannot be his nephew's photograph because a nephew would be a child of the speaker's sibling, and the speaker explicitly has no siblings.

It cannot be his uncle's or cousin's photograph, because the equation "that man's father is my father's son" clearly makes the speaker the father of the man in the picture, not a nephew or cousin.

Common Pitfalls:

Many examinees get tangled in "my father's son" and sometimes mistakenly think it refers to someone other than the speaker. The hint "I have no brother or sister" is included precisely to eliminate such confusion. Always substitute the simplified expression back into the original sentence and re-read it in plain language to avoid logical slips.

Final Answer:

The photograph is of the man's son.