GMAT Exercise 31
●Question 1. Sentence Correction
Direction: Correct the underlined part
By sucking sap from the young twigs of the hemlock tree, tree growth is retarded by the woolly adelgid, causing needles to change color from deep green to grayish green and to drop prematurely.
A. tree growth is retarded by the woolly adelgid, causing needles to change color from deep green to grayish green and to drop
B. tree growth is retarded by the woolly adelgid, and this causes the color of needles to change from deep green to grayish green, and their dropping
C. the woolly adelgid retards tree growth, which causes needles to change color from deep green to grayish green, and dropping
D. the woolly adelgid retards tree growth, causing needles to change color from deep green to grayish green and to drop
E. the woolly adelgid retards tree growth, and this causes the color of needles to change from deep green to grayish green, and then their dropping
●Question 2. Critical Reasoning
In parts of South America, vitamin-A deficiency is a serious health problem, especially among children. In one region, agriculturists are attempting to improve nutrition by encouraging farmers to plant a new variety of sweet potato called SPK004 that is rich in beta-carotene, which the body converts into vitamin A. The plan has good chances of success, since sweet potato is a staple of the region’s diet and agriculture, and the varieties currently grown contain little beta-carotene.
Which of the following, if true, most strongly supports the prediction that the plan will succeed?
A. The growing conditions required by the varieties of sweet potato currently cultivated in the region are conditions in which SPK004 can flourish.
B. The flesh of SPK004 differs from that of the currently cultivated sweet potatoes in color and texture, so traditional foods would look somewhat different when prepared from SPK004.
C. There are no other varieties of sweet potato that are significantly richer in beta-carotene than SPK004 is.
D. The varieties of sweet potato currently cultivated in the region contain some important nutrients that are lacking in SPK004.
E. There are other vegetables currently grown in the region that contain more beta-carotene than the currently cultivated varieties of sweet potato do.
●Question 3. Data Sufficiency
Directions: In this problem, a question is followed by two statements containing certain data. You are to determine whether the data provided by the statements are sufficient to answer the question. Choose the correct answer based upon the statement’s data and your knowledge of mathematics.
A. statement 1 alone is sufficient, but statement 2 alone is not sufficient to answer the question
B. statement 2 alone is sufficient, but statement 1 alone is not sufficient to answer the question
C. both statements taken together are sufficient to answer the question, but neither statement alone is sufficient
D. each statement alone is sufficient
E. statements 1 and 2 together are not sufficient, and additional data is needed to answer the question
●Question 4. Problem Solving
A jar contains 4 black marbles and 6 blue marbles. If you select 2 marbles from the jar, then what is the probability that one blue and one black marble will be picked?
A. 5/12 B. 3/4 C. 6/13 D. 7/15 E. 8/1
●Answer to Q1: D
Because of the preceding phrase ‘by sucking sap ~’ out of the line, ‘the woolly adelgid’ should be placed as the subject of the main clause in terms of the meaning. In this context, A and B are eliminated. In C, there is no expression that can be parallel with ‘dropping’, which is located right next to ‘and’. Also, the same error is being made in E. So, the answer is D.
●Answer to Q2: A
The statement is expecting the plan to succeed in terms of the nutrition and agricultural practice in the region. But it is ignoring the fact that the sweet potato called SPK004 may have different cultivating conditions that can affect the possibility of success. In this context, only A is supporting the prediction by mentioning that the cultivating conditions for the current sweet potatoes and SPK004 are the same. Therefore, the answer is A.
●Answer to Q3: D
The Question become to “ Is |x-y|^2>|x+y|^2 ? ==> Is x^2 -2xy+y^2>x^2+2xy+y^2 ? ==> 0>4xy? ==> xy>0?, therefore the best answer is D.
●Answer to Q4: E
4C1*6C1/10C2=4*6/(10*9/2!)=8/15, therefore the best answer is E.