GMAT考试Testprep数学精解_GMAT数学

GMAT考试Testprep数学精解

　　Logic II

　　Most arguments are based on some variation of an if-then statement. However，　the if-then statement is often embedded in other equivalent structures. Diagramming brings out the superstructure and the underlying simplicity of arguments.

　　If-Then

　　A――B

　　By now you should be well aware that if the premise of an if-then statement　is true then the conclusion must be true as well. This is the defining characteristic of a conditional statement; it can be illustrated as follows：

　　A――B

　　Therefore， B

　　This diagram displays the if-then statement A――B， the affirmed premise A， and the necessary conclusion B. Such a diagram can be very helpful in showing the logical structure of an argument.

　　Example：

　　If Jane does not study for the GMAT， then she will not score well. Jane， in　fact， did not study for the GMAT; therefore she scored poorly on the test.

　　When symbolizing games， we let a letter stand for an element. When symbolizing arguments， however， we may let a letter stand for an element， a phrase， a　clause， or even an entire sentence. The clause Jane does not study for the

　　GMAT can be symbolized as ~S， and the clause she will not score well can　be symbolized as ~W. Substituting these symbolssintosthe argument yields the following diagram：