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This is not a lsat kind of LG, because the lsat LG tests your deductive reasoning, that is, all the rules have been given in the stimulus.
This MS question is a reductive one, i.e. you need to find the rule by yourself.
The key is that if one plane can complete the journey, its oil tank must be full of oil when it finish at least half of the journey.
The steps for this question:
When there is only one plane, it can complete only half the whole journey. In fact, the earlier those planes that first drop drop, the less oil is consumed by them. This is the basic rule hidden behind the question. In the following reasoning, I assume the whole journey is 1 so a full tank of oil can complete only 1/2 of the whole journey.
In the case of two planes: When one of them drops, the plane that is full of oil needs to finish 3/4 of the whole journey. Obviously, it a mission impossible. (1-1/4=3/4)
In the case of three planes: When only one of them remains flying, it which is full of oil still needs to finish 7/12 of the whole journey. It is also a mission impossible. (1-(1/6+1/4)=7/12) When the plane that first drops drops, it finishes 1/6 of the whole journey. When the plane that secondly drops drops, it finishes 7/12 of the whole journey.
In the case of four planes: When only one of them remains flying, it which is full of oil still needs to finish 11/24 of the whole journey. That is possible. In fact, when the plane that finishes the whole journey lands, 1/24-tank of oil remains not consumed. (1-(1/8+5/12)=11/24)
In my opinion, the lesson which we can learn from the question and which is beneficial to solve a LG question, is to draw a hidden condition from those conditions expressly given in the stimulus.
[此贴子已经被作者于2005-3-25 19:58:58编辑过] | 
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发表于 2005-3-18 03:19:00
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