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198. 2^345+1的个位数是几(指数不太确定)
狗主人补充:就是看345能不能被4整除,然后对应到相应的尾数上去,然后再加1
<v2> 2^325(貌似是这个数字)+1的unit digit是哪个,选项有3,7,9神马的
思路:
最简单的尾数循环题目,分别是2, 4, 8, 6循环,345 mod 4 = 1,所以最后是2+1=3。
199. n (positive) is sum of consecutive integers, Is n/2 -5 greater than n/5-2?
(1) n is sum of five consecutive numbers
(2) n is no more than 40
思路:
假设n/2 -5 greater than n/5-2,则有n/2 -5 >n/5-2,n>10。
条件一:五个连续整数的和,跟10的关系不一定,如-1, 0, 1, 2, 3比10小。不充分。
条件二:不超过40,包含了大于10和小于10的范围,不充分。
两条件结合,仍旧不充分。选E。
200. in 2005, video cassettes are 3 times DVDs, total XX, in 2010, DVDs are 4 times video cassettes, total is 1,000, how much is the difference between DVDs in 2005 and in 2010?
思路:
In 2005, # of DVD = 0.25xx
In 2010, # of DVD = 4/5*1000 = 800
相减就行了。 |
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