[原创] 十月十六日 数学机井海外版 至101

yaomao

楼上，那是等差数列求和公式

donau

101. A bus traveled to its destination at speed of 60km/h. On the return trip, the bus traveled the same distance, but had an average speed of 80km/h, making the trip 2 hours shorter. What is the total distance of the round trip?

480km

这里是不是问双程的距离？如果这样的话应该480×2＝960

2000zlj

以下是引用yaomao在2006-10-16 12:56:00的发言：
楼上，那是等差数列求和公式

懂了，应该是a1=1,d=1时的等差数列求和公式吧？

dot_deng

以下是引用yaomao在2006-10-16 12:49:00的发言：
大家动作的都很快的说
94题该选A吧，
standard deviation<range/2

请问，这个是什么定理吗，我怎么从来没有听说过啊？

marvelvaliant

99. Does 8x=16+2x?
1). -3x is greater than or equal to -9
2). 2x is greater than or equal to 6

B

这题的提干是等号吗？如果是等号，我选E，条件一二都是不等式，存在很多可能，怎么能保证一个等式呢？

我想是不是提干也是不等式，8x>16+2x，如果是这样我选B。请指教！

marvelvaliant

以下是引用donau在2006-10-16 13:12:00的发言：

101. A bus traveled to its destination at speed of 60km/h. On the return trip, the bus traveled the same distance, but had an average speed of 80km/h, making the trip 2 hours shorter. What is the total distance of the round trip?

480km

这里是不是问双程的距离？如果这样的话应该480×2＝960

赞成，round trip是往返，谢谢提醒！

yaomao

99. Does 8x=16+2x?
1). -3x is greater than or equal to -9
2). 2x is greater than or equal to 6

根据条件2，等式肯定就不能成立了，
充分条件啊

Cantaloupe

从94题受益匪浅。谢一个！

taojm2001

99. Does 8x=16+2x?
1). -3x is greater than or equal to -9
2). 2x is greater than or equal to 6

From -3x>=-9, X>=3

From 2x>=6, X<=3

From Both x=3

So, my answer is C

taojm2001

95. Set S consists numbers arranged in ascending order. A new set is created as the follows: each elements of S is increased by a value equal to that number's place within the set. By how much is mean of new set greater than mean of the original set?
1). S consists of 10 elements.
2). The sum of the elements in the original set is 100

my answer is (D), A is right. B is same, because the new sum would be 100+, and the numbers are same, of course its mean is greater than that of the original set.