2. Prove that when a two digit number is divisible by 3, reversing its digits will also give a number divisible by 3.
there are only 30 two-digit numbers divisible by 3.
12, 15, 18, 21, 24, ... 93, 96, 99
reversing these digits give:
21, 51, 81, 12, 42, ... 39, 69, 99
these numbers are also divisible by 3, so the conjecture has been proved.
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