攒RP贴！！应要求改为大家攒RP贴 讨论数学问题 帮忙解答或提出疑问 LZ 不是NN 但做最大的努力帮大家解答数学问题。

yyx

請教97樓 四題~~~

-- by 会员 chasechase12 (2010/10/23 17:39:08)

lz回来答题了 之前一直在自己看资料神马的

yyx

感激啊!!




1.If it took Tom 0.5hour to cycle from his house to the library. was the distance that he cycled greater than 6 miles?

  (1) the average speed at which Tom great than 16 feet per second.
  (2) the average speed at which Tom less than 18 feet per second.

 ANS:E

2.If a certain sample of data has a mean of 20 and a standard deviation of 3. which of the following values is more than 2.5 standard deviation from the mean.

ANS: 12

3.How many hours did it take Tom to drive from her house to her parent's home?

  (1)Tom's average speed on this trip was 72km per hours.
  (2)If Tom's average speed on this trip had been 8km per hour greater, it would take her 1 hour less.    ANS:  C

4.Alice's take-home pay last year was the same each month, and she saved the same fraction of her take-home pay each month. The total amount of money that she had saved at the end of the years was 3 times the amount of that portion of her monthly take-home pay that she did not save. If all the money that she saved last year was from her take-home pay. what fraction of her take-home pay did she save each moth?

ANS: 1/5

-- by 会员 chasechase12 (2010/10/23 15:30:55)

第一题： 应该给出feet和miles 的换算 然后速度乘以时间比较答案
第二题：前面也有人问过 就是一个区间的问题就是20+-2.5*3  我把解答连接找出来等下贴上
第三题：条件一条件二不能单独得出答案。 但是假设全程s s/72-s/80=1可以算出答案
第四题：假设每个月工资为1 节省的比例是a 那么用掉的就是不节省的是1-a 根据题意一年一共节省12a 每个月不节省的是1-a 所以12a=3(1-a)     15a=3 a=1/5

yyx

If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than
2.5 standard deviations from the mean?

(A) 12.0
(B) 13.5
(C) 17.0
(D) 23.5
(E) 26.5

请教~完全看不懂问题。。more than
2.5 standard deviations from the mean 是什么意思？

-- by 会员 BlackTTea (2010/10/17 10:57:23)

我好像做到过，是问选项在不在20加减（2.5乘以3）的区间里，就是（12.5，27.5）.只有A不在

-- by 会员 Pudgysphere (2010/10/17 11:05:57)

就是这个题目

runnoo

就等于问从0到10里选3个数有多少种不同的和，最大的8+9+10=27，最小的0+1+2=3，所以3到27一共25个数

runnoo

lz好人~~


如果集合N 表示2^10 的所有因子，那么从里面选出P,Q,R,三个数的乘积，不同的情况有多少种
因子有2^0,2^1,2^2.......................

选项 25,28,29,30,31
答案25

是怎么的出来的 不解啊~~~~~

-- by 会员 lxw19 (2010/10/15 18:35:06)

就是求从0 到10 选三个数的和有多少个不同的，最大的8+9+10=27，最小的0+1+2=3，从3到27 一共25个数。

yyx

lz好人~~


如果集合N 表示2^10 的所有因子，那么从里面选出P,Q,R,三个数的乘积，不同的情况有多少种
因子有2^0,2^1,2^2.......................

选项 25,28,29,30,31
答案25

是怎么的出来的 不解啊~~~~~

-- by 会员 lxw19 (2010/10/15 18:35:06)

就是求从0 到10 选三个数的和有多少个不同的，最大的8+9+10=27，最小的0+1+2=3，从3到27 一共25个数。

-- by 会员 runnoo (2010/10/24 16:49:21)

嗯嗯 就这样得到 这题我已经解答了

Eileenl

http://forum.chasedream.com/GMAT_Math/thread-493159-1-1.html
这几题，不大懂题意，拜托LZ翻译和解答下啊~

ameliewoo

LZ 看看这个
86: m<n，求n(大概是这样的）
（1）最小公倍数为36
（2）最大公约数12
我选的是C
条件一，最小公倍数是36，m和n的组合可能是4,9；1,36. 求不出来
条件二，最大公约数是12，m和n的组合可能是1,12；12,24. 求不出来
两个条件结合，m和n唯一确定，12, 36。
选C

为什么条件二里说，最大公约数的组合可以使1,12？？   1 可以约掉12嘛？  不懂

pearlpeiwen

A chemist must add pure alcohol to a 100-liter solution that is 15
percent alcohol in order to produce a solution that is 20 percent
alcohol. How many liters of pure alcohol are needed?

(A) 9/2
(B) 5
(C) 25/4
(D) 10
(E) 100/7


If a high school were to sell t tickets for a charity hockey game,
the total revenue from ticket sales would be 25 percent greater than
the total costs of putting on the game. If the school sold all but 10
percent of the t tickets, the total revenue from ticket sales would be
what percent greater than the total costs of putting on the game?

(A) 2.5%
(B) 10%
(C) 12.5%
(D) 15%
(E) 16%


謝謝你 我想了好久 都不知道怎麼算

yiyisue

Q26:
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.
KEY:B
    
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.
E
THANKS！