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Number Theory
Level
2
\[\begin{eqnarray} 23 \times 64 = 32 \times 46 \\ 36 \times 42 = 63 \times 24 \\ 26 \times 31 = 62 \times 13 \end{eqnarray} \]
We call a pair of 2-digit positive integers reversible if their product remains the same when we reverse the digits in both integers.
The above shows that the pairs \((23,64), (36,42), (26,31) \) are reversible.
Which of the following is not reversible?
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by
Fidel Simanjuntak