Help me!

janep78

x和y都是两位数的正整数,x>y吗?
1.x的十位数大于y的个位数
2.x的个位数大于y的个位数

10^n+y被3除的余数为几?
1.n=5   2.y=2

lisaislisa

1 .E
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just with the proposition that both the tenth and unit of x is larger than the unit of y does not promise x is larger or smaller than y
eg x=34 y=21 and x=34 y=41

2.B
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whatever n is 10^n divides 3 remain 1
^^

janep78

what wrong with N=5?

卧室春竹

n=5  但是不知道 y=????

janep78

Oh,I know .
我一直把它看成(10^n+y),其实应该是(10^n)+y,对吧?

VICTOR_JZG

2.
如果把它看成10^(n+y),那么选D.因为10^(X)/3肯定余1了;

其实应该是(10^n)+y,则,应该选B.因为(10^(X)+2)/3肯定余0了,条件2已经充分了.
注意:这里容易错选为C. C表示条件1单独不充分,条件2单独不充分,而条件1和2联合才充分.此处条件2就已经充分,所以选B.

[此贴子已经被VICTOR_JZG于2003-1-5 21:06:02编辑过]

janep78

thanks .