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UKMT Junior Mathematical Challenge, 2015

Number theory Difficulty 1.0 Junior Find the answer United Kingdom

The result of the calculation $123456789 \times 8$ is almost the same as $987654321$ except that two of the digits are in a different order. What is the sum of these two digits?

(A) $3$ (B) $7$ (C) $9$ (D) $15$ (E) $17$

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