# Using Common Knowledge on GMAT Critical Reasoning

##### December 27, 2013

Here is a very simple argument:

A – B = C. Over time, A has increased. Therefore, C has increased.

If the argument seems simplistic, that’s because it is—it’s not very test-like or very challenging. It gives evidence about changes in A and concludes about a change in C; the assumption (the missing piece necessary for the conclusion to be logical) is that B has not also increased. After all, if A went up but B went up as well, who knows what C will turn out to be!

But this simple example underlines a pattern that can turn into big points on Critical Reasoning questions. The GMAT testmakers expect students to understand certain common knowledge. And some of that common knowledge takes the form of simple three-part equations just like the one above. For instance:

Revenue – Cost = Profit

Price * Sales = Revenue

Imports – Exports = Trade Deficit

Spending – Revenue = Budget Deficit

Wage * Time Worked =  Total Salary

A very common Critical Reasoning argument is to state that, based on evidence of a change of only one of the terms on the left, the term on the right must also change. The assumption, as we just saw, is that a change to the other left-hand term won’t counteract the effects of the first. Keep your eyes peeled for this opportunity to quickly increase your accuracy and timing on the Verbal section. Try to spot the problem in the following question:

Increasingly, American businesses requiring customer service phone lines have been utilizing overseas companies that can provide these services at extremely reduced rates.  Toll-free calls are routed to countries like India, where low-paid workers have been trained to deal with most of the typical problems consumers have with their credit cards, online services, and computer equipment. Since the companies using these overseas call centers are saving so much money, they will undoubtedly show higher profits than companies that do not.

Which of the following, if true, most seriously weakens the argument?

• (A) There is strong competition among overseas call centers to provide the most comprehensive services at the lowest rates.
• (B) Consumers opposed to exporting American jobs are willing to pay more for goods and services from companies that don’t engage in this practice.
• (C) Certain banking services cannot be outsourced, since this would require the release of customer financial data.
• (D) Because offshore telephone customer service companies provide only these services, they can train their employees more thoroughly than the American companies could.
• (E) Some American companies send their own employees overseas to train the call center personnel in their particular businesses

So, what do you think? Tell us your answers in the comments, and we’ll share the solution in an upcoming blog post. Good luck!