求助几道天山－3数学题

WTO

1， In the decimal representation of x, where 0<x<1, is the tenths digit if x nonzero?

1) 16x is an integer 2) 8x is an integer 答案是C. 没有思路，没看懂问题

2，For any integer K greater than 1, the symbol k* denotes the product of all the fractions of the form 1/t, where is an integer between 1 and k, inclusive. what is the value of 5*/4*?

A 5 B 5/4 C 4/5 D 1/4 E1/5 没看懂题意

3. What is the remainder when the positive integer x is divided by 8?

1)when x is divided by 12, the remainder is 5

2)when x is divided by 18, the remainder is 11

一直不太会做这种题，想知道思路

4， What is the value of the integer n?

1) n(n+2)=15 2)(n+2)^n=125 我认为应选D。 任何一个都可求出n=3. 而不是答案C.

谢谢了！祝大家好运！

mikejia

1。 1) 16x is an integer x可能是1/2=0.5， 1/4-=0.25， 1/8=0.125， 1/16=0.0625。所以十分位可能0，可能1，2，5。

2) 8x is an integer x可能 1/2=0.5， 1/4-=0.25， 1/8=0.125，所以十分位非零

2。（1/1*1/2*1/3*1/4*1/5）/（1/1*1/2*1/3*1/4）=4！/5！=1/5

后面还没算好

mikejia

3. What is the remainder when the positive integer x is divided by 8?

1)when x is divided by 12, the remainder is 5

(12a+5)/8=[8a+(4a+5)]/8 a=1,2,3....代入，说明不唯一

2)when x is divided by 18, the remainder is 11

（18b+11）/8=[16b+8+(2b+3)]/8 余数结果不唯一

both: 12a+5=18b+11 , 也不唯一。

4. n=负数！