求NN解答两题数学

caijilei · 发表于 2013-8-2 22:14:26

都是GWD2的但找不到解题方法很是郁闷
Q24

The valueof (9´107)(9´108)is closest to which of the following?

A. 1016

B. 1017

C. 1056

D. 1057

E. 1058

这题为什么答案是B 我想了半天都是A啊

Q25

A certain roller coaster has 3 cars, and a passenger is equallylikely to ride in any 1 of the 3 cars each time that passenger rides the rollercoaster. If a certain passenger is toride the roller coaster 3 times, what is the probability that the passengerwill ride in each of the 3 cars?

A. 0

B. 1/9

C. 2/9

D. 1/3

E. 1

排列组合真心硬伤求详解
Q32

What is the remainder when the two digit, positive integer x isdivided by 3?

(1) Thesum of the digits of x is 5.

(2) Theremainder when x is divided by 9 is 5.

A.Statement (1) ALONE is sufficient, but statement (2) alone is notsufficient.

B.Statement (2) ALONE is sufficient, but statement (1) alone is notsufficient.

C.BOTH statements TOGETHER are sufficient, but NEITHERstatement ALONE is sufficient.

D.EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOTsufficient.

求指导，谢谢！

caijilei · 发表于 2013-8-2 22:24:24

啊发现第一题选项应该是10^16, 10^17,

lhz910216 · 发表于 2013-8-3 11:14:07

(1)    (9*10^7)(9*10^8)=81*10^15=8.1*10^16\
因8.1距离10较近，故close to 10*10^16=10^17                B

(2)有3辆车，一个passenger每次坐一辆，问三次分别把这3辆都坐过的概率：
总的坐法有3*3*3=27 因每次都有3辆车可以选
样本：第一次坐，3选一，3种；第二次坐，不能和前一次重复，只能在余下的2个2选一，2种，最后一次只有一个选择  故 3*2*1=6
6/27=2/9                C

（3）第一个条件，和是5，就4个数，14，41，23，32 除以3余数都是2，OK
   第二个条件，x被9除余5，那x=9a+5（a设是商，是整数）  x/3=(9a+5)/3  9a可被3整除，但5被3除余2，所以余数就是2，  OK
选D

caijilei · 发表于 2013-8-3 14:47:32

lhz910216 发表于 2013-8-3 11:14
(1) (9*10^7)(9*10^8)=81*10^15=8.1*10^16\
因8.1距离10较近，故close to 10*10^16=10^17 ...

非常感谢！！帮大忙了！

求NN解答两题数学

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