Explaining a CR Discrepancy
Going for 90th+ percentile on verbal? Chances are youve spent most of your Critical Reasoning study time focused on the major question types, and that is a good place to start. If youre going for a very high verbal score, though, then youll also need to tackle the minor question types.
Thats what were going to do today; below is a GMATPrep CR problem. Give yourself about 2 minutes to do this problem.
In Asia, where palm trees are non-native, the trees flowers have traditionally been pollinated by hand, which has kept palm fruit productivity unnaturally low. When weevils known to be efficient pollinators of palm flowers were introduced into Asia in 1980, palm fruit productivity increasedby up to 50 percent in some areasbut then decreased sharply in 1984.Which of the following statements, if true, would best explain the 1984 decrease in productivity?
(A) Prices for palm fruit fell between 1980 and 1984 following the rise in production and a concurrent fall in demand.(B) Imported trees are often more productive than native trees because the imported ones have left behind their pests and diseases in their native lands.
(C) Rapid increases in productivity tend to deplete trees of nutrients needed for the development of the fruit-producing female flowers.
(D) The weevil population in Asia remained at approximately the same level between 1980 and 1984.
(E) Prior to 1980 another species of insect pollinated the Asian palm trees, but not as efficiently as the species of weevil that was introduced in 1980.
(Note: if you arent yet familiar with the 4-step process for answering CR questions, take a look at this article.)
Step 1: Identify the Question
This question stem contains the classic clues for an Explain a Discrepancy question. These questions, like Strengthen and Weaken questions, typically include the words if true (or the equivalent). Further, the question literally asks what would explain something.
Step 2: Deconstruct the Argument
All right, this is a Discrepancy question. The argument wont contain a conclusion. Itll contain some facts, at least one of which is surprising in some way. It wont fit with the rest of the information.
Heres what I thought and wrote while I did the problem. Your own thought process wont be exactly the same as mine and, of course, your notes will probably look quite different, since we all have our own ways of abbreviating things. (Note: ED = Explain Discrepancy)
Step 3: State the Goal
This is a Discrepancy question, so I have to find the thing that doesnt fit in the argument and figure out what new piece of information would help the argument make sense.
In this case, the introduction of the weevils worked at first, but then production dropped again for no apparent reason. There must be some reason why, and Ive already brainstormed one: maybe something happened in 1984 to cause a bunch of the weevils to die, so they were no longer able to pollinate the trees at the same level.
Work from Wrong to Right
The correct answer is C.
Notice that wrong answer (D) did address the weevil populationjust not in a way that would help explain the story. Answer (A) is also tricky. It provided a detail that made sense with the story, but that detail didnt answer the specific question asked: why productivity decreased in 84.
Take-aways for CR Discrepancy questions:
(1) The question stem will usually contain the words if true along with a request to explain something.
(2) Once you realize you have a Discrepancy question, look for the surprising event or disconnect in the argument. The correct answer is going to hinge on this!
(3) Watch out for trap answers that do go along with the argument but dont specifically explain the discrepancy (like answer A in this problem). Also watch out for trap answers that seem to address the detail at issue, but instead just make the surprising event even more surprising (like answer D in this problem).
* GMATPrep questions courtesy of the Graduate Management Admissions Council. Usage of this question does not imply endorsement by GMAC.