I would insert values 0-9 and divide by three, adding those numbers that give whole number answers.
31026/3 = 10342 (That's one.)
The five-digit number 31d26
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is divisible by 3. Find the sum of
all possible values of d.
2 answers
d must be divisible by 3, it must be 0,3,6,9 the sum is 18