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UKMT Junior Mathematical Challenge, 2020

Number theory Difficulty 2.0 Junior Find the answer United Kingdom

The digits of both the two-digit numbers in the first calculation below have been reversed to give the two-digit numbers in the second calculation. The answers to the two calculations are the same. $62 \times 13 = 806$ , $26 \times 31 = 806$ . For which one of the calculations below is the same thing true?

(A) $25 \times 36$ (B) $34 \times 42$ (C) $54 \times 56$ (D) $42 \times 48$ (E) $32 \times 43$

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