PP-DS171

[max999]

If k is a positive integer and the tens digit of k + 5 is 4, what is the tens digit of k ?
(1) k > 35
(2) The units digit of k is greater than 5.

answer: B
麻煩大家了

[amyliang]

上次做這題也錯了
舉例k=36 or 41
(1) if K=36+5=41 ..original ten is 3
if K=41+5=46 original is 4
(2) if K=36+5=41 the original ten is 3
if k =46+5=51 but k is a positive integer and the tens digit of k + 5 is 4, 所以不合
答案b