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UKMT Grey Kangaroo, 2024

Combinatorics Difficulty 2.0 Junior Find the answer United Kingdom

Ria has three counters marked $1$ , $5$ and $11$ , as shown. She wants to place them side-by-side to make a four-digit number. How many different four-digit numbers can she make?

(A) $3$ (B) $4$ (C) $6$ (D) $8$ (E) $9$

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