狒狒17题求助

sophialj

m is two digit number and 2m is a three digit number,what is the unit digit of m?

(1)the unit number of 2m is 4

(2)the unit number of m is the same as the tens number of 2m

答案是e,我觉得是B,大家能指点下我哪错了吗?

[此贴子已经被作者于2009-6-22 11:02:58编辑过]

justbp

m是2位数，2m是3位数，问的是m的个位数和2m十位数相等，

举个例子吧：m=62 2m=124; m=87 2m=174, 即使同时满足1+2，还是多余一个确定的数。

所以选E。