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GRE數學想考滿分？這6大失分點要關注
時間：2020-08-11
來源：網絡
作者：admin
相較于Verbal，GRE的Quantitative部分是絕大多數同學的得分利器，大家的目標也基本都鎖定在168+，甚至于滿分。雖然GRE數學考察的內容相對來說比較容易，但想要考一個滿分也并不如想象中的那么輕而易舉。尤其近年來，難題、坑題出現的頻率逐漸變高，考生在考場上一不小心就會失分。
一、沒有仔細讀題
例題
Of the students in a school, 20 percent are in the science club and 30 percent are in the band. If 25 percent of the students in the school are in the band but are not in the science club, what percent of the students who are in the science club are not in the band?
A. 5% B. 20% C. 25% D. 60% E. 75%
比如上面這題,問的是在science club的學生中不在band里面的百分比, 所以得用15%/20%=75%, 而不是直接等于15%.
二、幾何題中主觀做出題目沒給出的假設
例題：∠C=89°.
Quantity A: Length of AB
Quantity B: Length of BC
A. Quantity A is greater.
B. Quantity B is greater.
C. The two quantities are equal.
D. The relationship cannot be determined from the information given.
答案是D，因為在GRE數學考試中并不保證圖形會按照相應的比例繪制：there’s no guarantee that a figure will be drawn to scale on the GRE.
三、忘記 0 和 1
例題：If x is an odd negative integer and y is an even integer, which of the following statements must be true?
I. (3x - 2y) is odd
II. xy2 is an even negative integer
III. (y2-x) is an odd negative integer
A. I only
B. II only
C. I and II
D. I and III
E. II and III
答案: A. 容易錯選C, 如果y是0, xy^2就不是negative integer.
四、忘記最小的質數
例題
n is an even integer.
Quantity A: The number of prime factors of n
Quantity B: The number of prime factors of n/2
A. Quantity A is greater.
B. Quantity B is greater.
C. The two quantities are equal.
D.The relationship cannot be determined from the information given.
答案: D. 最小的質數是2,也是唯一的偶數。當n=2 的時候, Quantity A 是一個prime factor, Quantity B是0個prime factor當n=4的時候, Quantity A和Quantity B相等
五、沒有區分“must be” and “could be”
例題
c and d are prime numbers. If c – d is an odd integer, then which of the following must be true?
A) c is even
B) d is odd
C) c*d is odd
D) d is even
E) c*d +1 is odd
因為c和d都是prime且要滿足c-d是odd, 說明c和d一個是odd, 一個是even. 在所有prime中只有2是even, 所以c和d中一定有一個是2. 選項中 A,B,D都是could be true, C選項 c*d 一定是even. 所以答案選E.
Must be = Always correct
Could be = answer only holds true in certain instances
六、沒有注意符號單位
例題
Quantity A: 0.05 percent of 4000
Quantity B: 1/200 of 4000
A. Quantity A is greater.
B. Quantity B is greater.
C. The two quantities are equal.
D. The relationship cannot be determined from the information given.
計算的時候 percent 需要除以100, 所以0.05 percent of 4000= 0.05*4000/100 = 2, 所以答案選B。
遇到以上六種情況，同學們一定要保持警惕、多多思考。找出陷阱，直擊正確選項！
一、沒有仔細讀題
例題
Of the students in a school, 20 percent are in the science club and 30 percent are in the band. If 25 percent of the students in the school are in the band but are not in the science club, what percent of the students who are in the science club are not in the band?
A. 5% B. 20% C. 25% D. 60% E. 75%
比如上面這題,問的是在science club的學生中不在band里面的百分比, 所以得用15%/20%=75%, 而不是直接等于15%.
二、幾何題中主觀做出題目沒給出的假設
例題：∠C=89°.
Quantity B: Length of BC
A. Quantity A is greater.
B. Quantity B is greater.
C. The two quantities are equal.
D. The relationship cannot be determined from the information given.
答案是D，因為在GRE數學考試中并不保證圖形會按照相應的比例繪制：there’s no guarantee that a figure will be drawn to scale on the GRE.
三、忘記 0 和 1
例題：If x is an odd negative integer and y is an even integer, which of the following statements must be true?
I. (3x - 2y) is odd
II. xy2 is an even negative integer
III. (y2-x) is an odd negative integer
A. I only
B. II only
C. I and II
D. I and III
E. II and III
答案: A. 容易錯選C, 如果y是0, xy^2就不是negative integer.
四、忘記最小的質數
例題
n is an even integer.
Quantity A: The number of prime factors of n
Quantity B: The number of prime factors of n/2
A. Quantity A is greater.
B. Quantity B is greater.
C. The two quantities are equal.
D.The relationship cannot be determined from the information given.
答案: D. 最小的質數是2,也是唯一的偶數。當n=2 的時候, Quantity A 是一個prime factor, Quantity B是0個prime factor當n=4的時候, Quantity A和Quantity B相等
五、沒有區分“must be” and “could be”
例題
c and d are prime numbers. If c – d is an odd integer, then which of the following must be true?
A) c is even
B) d is odd
C) c*d is odd
D) d is even
E) c*d +1 is odd
因為c和d都是prime且要滿足c-d是odd, 說明c和d一個是odd, 一個是even. 在所有prime中只有2是even, 所以c和d中一定有一個是2. 選項中 A,B,D都是could be true, C選項 c*d 一定是even. 所以答案選E.
Must be = Always correct
Could be = answer only holds true in certain instances
六、沒有注意符號單位
例題
Quantity A: 0.05 percent of 4000
Quantity B: 1/200 of 4000
A. Quantity A is greater.
B. Quantity B is greater.
C. The two quantities are equal.
D. The relationship cannot be determined from the information given.
計算的時候 percent 需要除以100, 所以0.05 percent of 4000= 0.05*4000/100 = 2, 所以答案選B。
遇到以上六種情況，同學們一定要保持警惕、多多思考。找出陷阱，直擊正確選項！
