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标题: 求救：一道prep数学题DS [打印本页]

作者: sherryxq 时间: 2007-12-2 21:12
标题: 求救：一道prep数学题DS

When positive integer n is divided by 3, the remainder is 2; and when positive integer t is divided by 5, the remainder is 3. What is the remainder when the product nt is divided by 15?

(1)n-2 is divisible by 5

(2)t is divisible by 3

作者: cc101010 时间: 2007-12-2 21:19
刚算错

[此贴子已经被作者于2007-12-2 21:24:04编辑过]

作者: cc101010 时间: 2007-12-2 21:24

不好意思，算错了

作者: cc101010 时间: 2007-12-2 21:25

Ｃ各～

作者: cc101010 时间: 2007-12-2 21:28

题目中条件n=3A+2 t=5B+3

由条件１得，n=5C+2. 又n=3A+2　　所以Ａ＝５S,则n=15s+2

由条件２得，t=3D.结合题目条件t=5B+3　　说明Ｂ是３的倍数，即Ｂ＝３k．　则t=１５k+3

单独均不可推，合以来可推　６

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