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Problem 81

Combinatorics Difficulty 1.0 Find the answer UKMT Junior Mathematical Challenge · United Kingdom · 2025

Ibraheem has $10$ cards. Four display the letter P; three display Q; two display R and one displays S. He also has $10$ counters. One shows the number $3$ ; two show $1$ ; three show $4$ and four show $2$ . He places one counter on the top of each card so that every pairing is different. Which one of these pairings does he not make?

(A) P2 (B) R4 (C) Q1 (D) R2 (E) S4

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