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4月14日 GMAT数学逻辑每日一练

原标题:4月14日 GMAT数学逻辑每日一练

4月14日 GMAT数学逻辑每日一练

【数学】

Pumps A, B and Coperate at their respective constant rates.Pumps A and B, simultaneously, canfill a certain tank in 6/5 hours. Pump A andC, operating simultaneously, canfill the tank in 3/2 hours; abd pumps B and C,operating simultaneously, canfill the tank in 2 hours. How many hours does ittake pumps A, B, and C, operating simultaneously, to fill the tank?

(A) 1/3

(B) 1/2

(C) 2/3

(D) 5/6

(E) 1

【逻辑】

Which of the following most logically completes theargument? A recent poll found that over 80 percent of the residents of NalmedProvince favoreda massive expansion of the commuter rail system as a means of significantlyreducing congestion on the province's highways and were willing to help pay forthe expansion through an increase in their taxes. Nevertheless, the pollresults contain an indication that expansion of the rail system, ifsuccessfully completed, might be unlikely to achieve its goal of reducingcongestion, because________________.

A. most people in favor of expanding the railsystem reported less congestion during their highway commuteas the primarybenefit they would experience

B. of the less than 20 percent of residentsnot counted as favoring the expansion, about half claimed to have no opinionone way or the other

C. the twice-dairy periods of peak congestioncaused by people commuting in cars have grown, over the past 20years, fromabout an hour each to about two hours each

D. expanding the commuter rail system willrequire the construction of dozens of miles of new bed

E. the proposed expansion wouldmake commuting by rail possible for many people who Eve in one suburb and work ina different suburb of the province's main city.

答案

【数学】

题目翻译:水泵 A、B、C,若 A、B 共同抽水,1.2 小时抽完;若 A、C 共同抽水,1.5 小时抽完;若 B、C 共同抽水,2 小时抽完,问若三个共同抽水,多长时间抽完?

思路点拔:把时间转换成效率再计算

题目全解:设 A、B、C的效率分别是 A、B、C,则 A+B=5/6,A+C=2/3,B+C=1/2,三式相加得,2(A+B+C)=2,A+B+C=1。

选 E。

【逻辑】

Reasoning

What most supports the claim that the poll data indicatethat the rail system expansion may not reduce congestion? The expansion willnot reduce highway congestion unless it results in fewer people driving duringcongested periods, such as rush hours when many people commute. Therefore, lookfor an answer option that takes the poll results as suggesting that not manydrivers would switch to commuting on the expanded rail system.

A. Correct. This shows that the poll dataindicate that most of the residents who favor the new rail system plan to keepcommuting by car—thus still contributing to highway congestion.

B. The fact that 10 percent of the residents"have no opinion" provides no evidence that the poll data indicatethe rail system expansion would not reduce congestion.

C. The claim that the time needed for dailycommutes has doubled says nothing at all about the interpretation of the polldata—and therefore nothing about what the poll data might indicate about thepossible failure of the rail expansion to reduce congestion. It isthmusirrelevant.

D. This claim says nothing at all about theinterpretation of the poll data and is incorrect because irrelevant.

E. This claim says nothing at allabout the interpretation of the poll data and is incorrect because irrelevant.

Thecorrect answer is A.

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