OG167 求解

yuyue0277

167. If n is a positive integer, what is the tens digit of n ?
(1) The hundreds digit of 10n is 6.
(2) The tens digit of n + 1 is 7.

DS部分 ，答案给的是：

(1) Given that the hundreds digit of 10n is 6,
the tens digit of n is 6, since the hundreds
digit of 10n is always equal to the tens digit
of n; SUFFICIENT.
(2) Given that the tens digit of n + 1 is 7, it is
possible that the tens digit of n is 7 (for
example, n = 70) and it is possible that the
tens digit of n is 6 (for example, n = 69);
NOT suffi cient.

条件就没看懂。The tens digit of n + 1  is 7 应该怎么理解？

小问孩

我觉得就是说 n + 1的十位数是7. 把n+1看做一个整体。

yuyue0277

哦，恍然大悟。。。多谢LS的MM