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Function: driver
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File: /volume1/web/PhpstormProjects/www_polymath_co_kr/application/libraries/Common.php
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Line: 559
Function: get_footer
File: /volume1/web/PhpstormProjects/www_polymath_co_kr/index.php
Line: 315
Function: require_once
수학동아 - 폴리매스
[수학 정보] 9의 단(아시는 분 알려주세요...)
엉금
2020.06.15 01:24
조회 931
9의 단은 항상 자릿수들의 합이 9인데 왜 11 곱하기 9만 합이 18이에요?
-
그건 자릿수 배수판정 때문입니다
9*10이 9의 최대죠?
9의 배수의 성질:
각자리수의 합이 모두 9의 배수이다
2자리수이하의 최대는
18입니다
또, 9*10 = 9가 최대입니다
따라서 그이전의 배수는 모두 9가되고
그다음부터는 모두 18이됩니다
12*9도 해보세요 자리수이 합이 18입니다 ㅎㅎ
그다음엔 27, 그다음엔 36........
-
수의 각 자리 수가 커서 그럽니다
그렇게 9가 아니게 나온 수를 다시 자릿수의 합이 1의 자리가 될 때까지 더해주면 모두 9가 됩니다
-
222
Lv.9
2020.06.22 05:08
모든 숫자는 항상 9가 됩니다. 예를 들면 18이 나왔을 때면 1+8 한번 더 하면 9가 나옵니다.
이걸 계속 반복하면 999999999999999999999999999999999 이런 수도 결국 9가 나옵니다^^
-
루트23
Lv.4
2020.06.27 05:53
그렇네요. 그래서 끝까지 봐 주시면 뿌리를 잡고 수들 모두가 9가 되는 것을 확인하실 수 있을 겁니다. 굉장히 어마어마한 수들도 계속 나누어 보신다면, 9의 배수) 모두가 9 로 끝맺는 것을 확인하실 수 있습니다
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