gmatsystems - Question#13(incorrect .Iftherewereno...

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Question #13 (incorrect) The neighborhood association planted 240 new trees last year. If there were no  other changes to the neighborhood's tree population, how many of the new trees  planted by the neighborhood association were elm trees? i. Of all the trees in the neighborhood, 40 percent were elm trees at the end of  last year. ii. At the beginning of last year, 20 percent of the trees in the neighborhood were  elm trees. e (A) Statement (1) ALONE is sufficient, but statement (2) alone is  not sufficient. n (B) Statement (2) ALONE is sufficient, but statement (1) alone is  not sufficient. n (C) BOTH statements TOGETHER are sufficient, but NEITHER  statement ALONE is sufficient.  your answer y (D) EACH statement ALONE is sufficient. ( (E) Statements (1) and (2) TOGETHER are NOT sufficient.  correct Explanation The question asks us how many of the new trees that a neighborhood  association planted last year were elm trees. Note that there are a number of different quantities we may have to consider. At  the beginning of last year, there were some elm trees () and some non-elm trees  (). These two quantities made up the total number of neighborhood trees (), so . At the end of last year, there were some elm trees () and some non-elm trees ().  These two quantities made up the total number of neighborhood trees, which  was  more than the number of neighborhood trees at the beginning of the year: .  Any number of these  new trees, from  to , could have been elm trees; if we can  solve either for    and  individually, or for the expression , we can find the number  of new elm trees. Statement 1 says that , or , of the trees in the neighborhood were elms at the end 
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of last year: . Cross multiply: . This is an equation with two unknowns. Even if we  could solve for both unknowns, we would have no information about how many of  the elms at the end of last year had been planted in the last year. Statement 1  alone is NOT sufficient to answer the question. Eliminate answer choices A and  D. The correct answer choice must be B, C, or E.
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