GMAT考试：Testprep数学精解2_GMAT数学

GMAT考试：Testprep数学精解2

　　/.9 = 1.2C

　　Since we now have only one equation involving the cost， we can determine the　cost by solving for C. Hence， the answer is A or D. is insufficient since it does not relate the selling price to any other　information. Note， the phrase initially listed implies that there was more　than one asking price. If it wasnt for that phrase， would be sufficien　

　　4. What is the value of the two-digit number x?

　　 The sum of its digits is 4.

　　 The difference of its digits is 4.

　　Considering only， x must be 13， 22， 31， or 40. Hence， is not sufficient to determine the value of x.

　　Considering only， x must be 40， 51， 15， 62， 26， 73， 37， 84， 48， 95， or 59. Hence， is not sufficient to determine the value of x.

　　Considering and together， we see that 40 and only 40 is common to the two sets of choices for x. Hence， x must be 40. Thus， together and　are sufficient to uniquely determine the value of x. The answer is C.

　　5. If x and y do not equal 0， is x/y an integer?

　　 x is prime.

　　 y is even.

　　 is not sufficient since we dont know the value of y. Similarly， is　not sufficient. Furthermore， and together are still insufficient since there is an even prime number2. For example， let x be the prime number