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UKMT Junior Mathematical Challenge, 2023

Number theory Difficulty 2.0 Junior Find the answer United Kingdom

Each cell in the crossnumber is to be filled with a single digit. Across: 1. A cube; 2. A square. Down: 1. A prime. The crossnumber grid has two rows of two cells each, labelled 1 (top-left cell) and 2 (bottom-left cell). Which of these could be the sum of the four digits in the crossnumber?

(A) $17$ (B) $16$ (C) $15$ (D) $14$ (E) $13$

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