GMAT PREP数学Data sufficiency考试难点总结参考.doc

PP- Data Sufficiency1 (DS1) 完整詳解版 Practice Test #1 Data Sufficiency (218 Questions) 1. 86-!-item-!-187;#058 A garden store purchased a number of shovels and a number of rakes. If the cost of each shovel was $14 and the cost of each rake was $9, what was the total cost of the shovels and rakes purchased by the store? (1) The ratio of the number of shovels to the number of rakes purchased by the store was 2 to 3. (2) The total number of shovels and rakes purchased by the store was 50. -------------------------------------------------------------------------------------------------------------------------------------------------------- 【答案】C 【思路】 設Qs為shovels的數量 設Qr為rakes的數量 題目問: 14Qs + 9 Qr =? (1) Qs=2a, Qr=3a ,只知比例,不知各為多少,無法求得數量,不充分 (2) Qs + Qr = 50,只知總和,不知各為多少,也無法求數total cost,不充分 (1)+(2) 將(1)代入(2)可得a=10 , 即Qs=20,Qr=30,所以total cost已經可以算出, 充分! -------------------------------------------------------------------------------------------------------------------------------------------------------- 2. 142-!-item-!-187;#058 Of the students who eat in a certain cafeteria, each student either likes or dislikes lima beans and each student either likes or dislikes brussels sprouts. Of these students,dislike lima beans; and of those who dislike lima beans, also dislike brussels sprouts. How many of the students like brussels sprouts but dislike lima beans? (1) 120 students eat in the cafeteria. (2) 40 of the students like lima beans. -------------------------------------------------------------------------------------------------------------------------------------------------------- 【答案】D 【思路】 beans ~ beans sprouts a b ~ sprouts c d t 註: ~代表dislike 設t為total students 設like beans like sprouts人數 為a 設dislike beans like sprouts人數 為b 設like beans dislike sprouts人數 為c 設dislike beans dislike sprouts人數 為d 已知d= 題目問: b=? (1) t= 120, 得知b+d=80且d=50, 所以得出b=30, 充分 (2) a+c = 40 = 得出t=120 同(1)也可以算出b, 充分 ---------------------------------------------------