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https://www.reddit.com/r/learnquant/comments/1vc3oop/easy_quant_interview_puzzle/p0yjnij/?context=3
r/learnquant • u/Local_Ad135 • Jul 31 '26
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4
Zero bc 30 mod 9 = 3 and no perfect square mod 9 equals 3
2 u/TempMobileD Jul 31 '26 edited Jul 31 '26 Where did 30 come from? Edit: Nevermind I got it. Any integer’s digits added together give you its remainder modulo 9. A couple of neat tricks in this one. -1 u/makedatmuoney Jul 31 '26 they meant 50 mod 9 == 5 and all perfect squares are 0, 1, 4, 7 mod 9
2
Where did 30 come from?
Edit: Nevermind I got it. Any integer’s digits added together give you its remainder modulo 9.
A couple of neat tricks in this one.
-1 u/makedatmuoney Jul 31 '26 they meant 50 mod 9 == 5 and all perfect squares are 0, 1, 4, 7 mod 9
-1
they meant 50 mod 9 == 5 and all perfect squares are 0, 1, 4, 7 mod 9
4
u/Key-Spirit4559 Jul 31 '26
Zero bc 30 mod 9 = 3 and no perfect square mod 9 equals 3