[求助]请高人指点，这两个题是不是答案错了啊？

JessieForGmat

好像很简单，但是算得都不是给出的答案呢，是我疏忽了哪里还是答案给错了？请大家帮忙看看吧。。。

176   Yesterday it took a certain plane 3 hours to fly from City A to City B at an average speed of 400 miles per hour. Today the same plane flew from City A to City B along the same route at

an average speed of 450 miles per hour. How many more yesterday than it took today?

A.      10

B.      15

C.      20

D.     25

E.      30

这个不是应该3*400得出1200miles，然后1200/450得到8/3小时，再用3-8/3就是多花的时间吗？应该是E啊，为什么选C呢？

177   In a certain quiz that consists of 10 questions, each question after the first is worth 4 points more than the preceding question. If the 10 questions on the quiz are worth a total of 360 points, how many points is the third question worth?

A.      18

B.      24 

C.      26 

D.     32  

E.      44

S10=10A1+（10-9/2）4=360 得出A1为18，那第三项不是应该是26吗？为什么是B呢？

谢谢。

[此贴子已经被作者于2007-11-29 9:48:14编辑过]

开若兰

QUOTE:

以下是引用JessieForGmat在2007-11-28 23:06:00的发言：

好像很简单，但是算得都不是给出的答案呢，是我疏忽了哪里还是答案给错了？请大家帮忙看看吧。。。

...

177   In a certain quiz that consists of 10 questions, each question after the first is worth 4 points more than the preceding question. If the 10 questions on the quiz are worth a total of 360 points, how many points is the third question worth?

A.18

B.24 

C.26 

D.32  

E.44

S10=10A1+（10-9/2）4=360 得出A1为18，那第三项不是应该是26吗？为什么是B呢？

谢谢。

我也认为这道题的正确答案应该是 C。

wangjianghua

同问！！