请教牛牛来解答 明天考试了 群里没有定论~~

雨中小熊呵

有一道DS 问a/b是否是terminating decimal（有限循环）
1. a=2^t  t是positive Integer
2. b=2^s  s是positive integer


本来大家一致认为选B的 但是后来有位同学意识到a的值不确定呀 比如a=1/3的时候 选B就不可以呀
所以大家目前的倾向是选C  
还请牛牛们给我们一个定论 明天就考试啦

雨中小熊呵

为嘛没有人回呢  自己顶~~

carey513

看下题目有没有说a,b是不是整数吧，到时候还是自己看下题目怎么说，应该不难，祝lz明天顺利破7啊！

wakjzmb

同时明天考试，注意看下条件啦。如果按没有提a,b是整数啥的，只能选C了

yoxsheila

见OG12--139
基本上是原题
139.  Any decimal that has only a finite number of nonzero digits is a terminating decimal. For example, 24, 0.82, and 5.096 are three terminating decimals. If r and s rare positive integers and the ratio r/s  is expressed as a decimal, is r/s  a terminating decimal?
(1) 90 < r < 100
(2)   s = 4
Arithmetic Properties of numbers
(1)This  is provides no information about the  value of s. For example, 92/5  = 18.4, which  terminates, but  92/3 = 30.666 . . . , which does not terminate; NOT sufficient.
(2)  Division by the number 4 must terminate: the remainder when dividing by 4 must be 0, 1, 2, or 3, so the quotient must end with .0, .25, .5, or .75, respectively;
SUFFICIENT.
The correct answer is B;
statement 2 alone is sufficient.

terminating decimal是有限小数，而不是有限循环。吧。。。

雨中小熊呵

看下题目有没有说a,b是不是整数吧，到时候还是自己看下题目怎么说，应该不难，祝lz明天顺利破7啊！

-- by 会员 carey513 (2010/9/26 22:06:47)

恩 了解~~希望借你吉言呀~·

雨中小熊呵

同时明天考试，注意看下条件啦。如果按没有提a,b是整数啥的，只能选C了

-- by 会员 wakjzmb (2010/9/26 22:08:03)

明天一起加油

yoxsheila

搞错了
我考虑的问题和你不一样。。
现在明白你的意思了。。
也在纠结
要不要选C...

雨中小熊呵

见OG12--139
基本上是原题
139.  Any decimal that has only a finite number of nonzero digits is a terminating decimal. For example, 24, 0.82, and 5.096 are three terminating decimals. If r and s rare positive integers and the ratio r/s  is expressed as a decimal, is r/s  a terminating decimal?
(1) 90 < r < 100
(2)   s = 4
Arithmetic Properties of numbers
(1)This  is provides no information about the  value of s. For example, 92/5  = 18.4, which  terminates, but  92/3 = 30.666 . . . , which does not terminate; NOT sufficient.
(2)  Division by the number 4 must terminate: the remainder when dividing by 4 must be 0, 1, 2, or 3, so the quotient must end with .0, .25, .5, or .75, respectively;
SUFFICIENT.
The correct answer is B;
statement 2 alone is sufficient.

terminating decimal是有限小数，而不是有限循环。吧。。。

-- by 会员 yoxsheila (2010/9/26 22:17:17)

你理解错我的意思了吧 ~~因为OG这题已经说了r and s rare positive integers

yoxsheila

见OG12--139
基本上是原题
139.  Any decimal that has only a finite number of nonzero digits is a terminating decimal. For example, 24, 0.82, and 5.096 are three terminating decimals. If r and s rare positive integers and the ratio r/s  is expressed as a decimal, is r/s  a terminating decimal?
(1) 90 < r < 100
(2)   s = 4
Arithmetic Properties of numbers
(1)This  is provides no information about the  value of s. For example, 92/5  = 18.4, which  terminates, but  92/3 = 30.666 . . . , which does not terminate; NOT sufficient.
(2)  Division by the number 4 must terminate: the remainder when dividing by 4 must be 0, 1, 2, or 3, so the quotient must end with .0, .25, .5, or .75, respectively;
SUFFICIENT.
The correct answer is B;
statement 2 alone is sufficient.

terminating decimal是有限小数，而不是有限循环。吧。。。

-- by 会员 yoxsheila (2010/9/26 22:17:17)

你理解错我的意思了吧 ~~因为OG这题已经说了r and s rare positive integers

-- by 会员 雨中小熊呵 (2010/9/26 22:20:09)

嗯，呵呵。。