one question for a september math problem?

gmat2002

DS m的个位数＝？（1）m+2个位数为9 (2) 2m 个位数为 4
【确定】 A

I have some questions about this one. If a number is -11, his unit m is -1 or 1??

Thanks!

tongxun

-9 的个位是9吗？我有点糊涂了。那位帮忙回答以下。

gmat2002

so it means for condition one
m + 2 unit is 9. m can be -11 or 7. So we can not confirm its unit number???

tongxun

yes，you are definately right， gansen。
-11， the digit of it is 1。

gansen

hi, gmat2002
i think if the number m=-11, its digit number is 1, so it doen't fit for the first condition. so the answer of this question should be A

tongxue, am i right?

tongxun

题目问的是m的个位数啊。7+2=9。能将你的问题写的更明确一些吗？