GMAT考试：Testprep数学精解2_GMAT数学

GMAT考试：Testprep数学精解2

C if the two statements TAKEN TOGETHER are sufficient to answer the question， but NEITHER statement ALONE is sufficient;D if EACH statement ALONE is sufficient to answer the question;E if the two statements TAKEN TOGETHER are still NOT sufficient to answer the question.

　　Numbers： Only real numbers are used. That is， there are no complex numbers.

　　Drawings： The drawings are drawn to scale according to the information given　in the question， but may conflict with the information given in statements

　　You can assume that a line that appears straight is straight and that angle　measures cannot be zero.

　　You can assume that the relative positions of points， angles， and objects are as shown.

　　All drawings lie in a plane unless stated otherwise.

　　Example：

　　In triangle ABC to the right， what is the value of y?

　　 AB = AC

　　 x = 30

　　Explanation： By statement ， triangle ABC is isosceles. Hence， its base angles are equal： y = z. Since the angle sum of a triangle is 180 degrees， we　get x + y + z = 180. Replacing z with y in this equation and then simplifying yields x + 2y = 180. Since statement does not give a value for x， we cannot determine the value of y from statement alone. By statement ， x= 30. Hence， x + y + z = 180 becomes 30 + y + z = 180， or y + z = 150. Since statement does not give a value for z， we cannot determine the value of y from statement alone. However， using both statements in combination，we can find both x and z and therefore y. Hence， the answer is C.