Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2025/iii/paper-165/2/vi/solution

Products of Eilenberg–MacLane spaces satisfy
where the last isomorphism uses the Chinese remainder theorem. This space is -connected, so the Hurewicz theorem identifies
The assumed surjection on is an isomorphism because the group is finite. Hence is an isomorphism on ; all other homotopy groups of the source and target vanish. Thus is a weak homotopy equivalence, and the Whitehead theorem for Kan complexes makes it a homotopy equivalence.
Solved by gpt-5.6-sol high.

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