救命啊 SHUXUE

guo573874201

1.If x is a positive integer, is the remainder 0 when 3^x + 1 is divided by 10?
(1)x = 4n + 2, where n is a positive integer.
(2)x > 4答案选A
2. If a code word is defined to be a sequence of different letters chosen from the 10 letters A, B, C, D, E, F, G, H, I, and J, what is the ratio of the number of 5-letter code words to the number of 4-letter code words?


A.5 to 4
B.3 to 2
C.2 to 1
D.5 to 1
E.6 to 1正确

3.  Which of the following fractions has a decimal equivalent that is a terminating decimal?
A 10/189     B 15/196   C16/225   D 25/144   E 39/128    有什么好方法可以看出来呢  


需要指点  谢谢了