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Ones, Twos and Threes

Age 11 to 14 Short
Challenge Level

Answer: 1112233


Digits include $1, 2, 3, 1, 2, 3$ and maybe more

$1+2+3=6$ so any number with digits $1, 2, 3, 1, 2, 3$ is a multiple of $3$
$\Rightarrow$ use another $1$

$1112233$ smallest possible with another $1$ and this is also odd



This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.