GAMT Prep pp 01-145 (DS)

[GC06]

On her way home from work, Janet drives through several tollbooths. Is there a pair of these tollbooths that are less than 10 miles apart?

(1) The first tollbooth and the last tollbooth are 25 miles apart.

(2) Janet drives through 4 tollbooths on her way home from work.


答案是C
我覺得是E耶 題目是要問我們什麼?
感謝解答!

[hey]

這題是問眾多的收費站中,其中的兩個收費站距離有沒有少於10哩?
條件一:只說第一個與最後一個的距離是25哩, 但不知中間到底有幾個, 可能很多個, 可能一個都沒有, 所以不充份
條件二: 只說有4個收費站, 但不知總距離為何, 所以不充份
條件一及條件二合起來就充份了, 因為總長25哩, 有4個收費站, 如果每個收費站間的距離是均等的話, 收費站之間則會是25/3<10, 但如果不均等的話, 則其中有距離較長的及距離較短的, 題目只要求其中兩個收費站的距於有沒有少於10哩, 所以最少一定會有一個間距少於10哩
所以選項(C)充份

[chris8888]

On her way home from work, Janet drives through several tollbooths. Is there a pair of these tollbooths that are less than 10 miles apart?

(1) The first tollbooth and the last tollbooth are 25 miles apart.

(2) Janet drives through 4 tollbooths on her way home from work.

(1) + (2).
四個tollbooths, 三個區間
|___|___|___|
A　　B　　C　D
假如AB = 10, BC = 10, CD = 5 一對低於10 miles
假如AB = 5, BC = 5, CD = 20 兩隊低於10 miles
假如AB = 10, BC = 10, CD = 10 ; 破30, 爆了

因此怎麼看都不可能全部都是超過10 miles的距離, 所以一定有至少一組是少於10 miles. 答案是C

如果題目給的是總長度30 miles,
有兩種可能 10+10+10 <== 沒有任何一對tollbooths低於10 miles
或 10 + 8 + 12 <== 可以有一對低於 10 miles
出現兩種歧異, 答案是E

[sunnyblue13s]

個人覺得...PP的答案應該不會是錯的...
唯一的假設可能是文化背景的差異性...產生了歧意...
ETS可能認知...每個收費站為"等距".....

唯有這樣~~答案才可能會是C....

唉....文化差異吧....

[Philosophia]

因為實在不太瞭解，google 了一下，發現在某網站上有人說明如下

A) insuff
B) insuff
A+B) We can arrange only 3 booths with atleast diff 10.
0---4---14---24-25
Let one more come any where in between , atleast one pair have the diff less than 10.

資料來料：http://www.urch.com/forums/gmat-data-sufficiency/68584-gmat-prep-question.html

所以，我想，若是那種下高速公路才依距離收費的方式來看的話，
(1) + (2) 全長25 miles，均分四段，每段將少於 10 miles.

Ans. C