GWD23-16

norgar

Q16:

If k is a positive integer, what is the remainder when 2^k is divided by 10 ?

(1)   k is divisible by 10.

(2)   k is divisible by 4.

              

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

Answer:   

为什么是B呢

carollai

2^10个位数为4，2^20个位数为6，后面一直是4和6重复，余数有两种情况：4和6，所以不充分

chriszhx

why the first condition is not sufficient??

chwayne

余数是6吧

berylgirls

 2^4=16,

16的任意次方，结果的个位都是6，被10除，余数都是6