Not bad
Number Theory
Level
4
What’s the smallest number that is divisible by 225 such that its decimal representation must consist of 1's and 0's only.
Clarification : You need to use both 0's and 1's.
The answer is 11111111100.
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1 solution
It takes a really extensive computer search to go through over ten billion numbers to find this one.
Or, since 225 = 9 x 25, use divisibility rules for 9 to get 11111111100. Eh.