Re: [中學] 一題國中數學
※ 引述《prophet4447 (爺)》之銘言:
題目是2012個1乘以2012個3所有位數的加總是多少…
答案是18102
是否有人能有神來一筆之解
請賜教謝謝
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這規律如何找的?
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01/22 01:07,
01/22 01:07
因為2013個才會被3整除
所以我改寫成111...111*333...333-10^2012*333...333
(2013個1) (2012個3)
=370370...37037*999...999 - 10^2012*333...333
(670組370)
=370370...37037*(10^2012-1)-10^2012*333...333
=370370...3704*10^2012 - 370370...37037
(670組370)
=370370...3703629629...62963
(670組370) (670組629)
故數字和=670*(3+7+6+2+9) + 3 + 6 + 3
=670*27 +12 = 18102
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