【正文】 43. 5768!item!187。004684 Six machines, each working at the same constant rate, together can plete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to plete the job in 8 days? (A) 2 (B) 3 (C) 4 (D) 6 (E) 8 【答案】 B 【思路】速率 x時間 =工作量 (距離 ) Sx12(days)=1,S= 112(six machines),表示一臺的速率172(這個地方要小心！！ ) 假設 x臺機器 plete the job in 8 days 1 172??X8＝,X=9,所以必須增加 3臺機器 plete the job in 8 days 41. 5676!item!187。004451 Three grades of milk are 1 percent, 2 percent, and 3 percent fat by volume. If x gallons of the 1 percent grade, y gallons of the 2 percent grade, and z gallons of the 3 percent grade are mixed to give x + y + z gallons of a percent grade, what is x in terms of y and z ? (A) y + 3z (B) (y + z) /4 (C) 2y + 3z (D) 3y + z (E) 3y + 39. 5583!item!187。004235 In a certain deck of cards, each card has a positive integer written on it. In a multiplication game, a child draws a card and multiplies the integer on the card by the next larger integer. If each possible product is between 15 and 200, then the least and greatest integers on the cards could be (A) 3 and 15 (B) 3 and 20 (C) 4 and 13 (D) 4 and 14 (E) 5 and 14 【答案】 C 【思路】 題意應該是抽一張牌就要乘上這張牌和其下一個號碼 所以 3x(3+1)=12. 4x(4+1)=20, 13x(13+1)=182, 14x(14+1)=210. 應該是 4與 13沒錯 37. 5000!item!187。004030 Of the following, which is least? (A) (B) ()2 (C) (D) (E) 35. 4632!item!187。003962 At a certain university, the ratio of the number of teaching assistants to the number of students in any course must always be greater than 3:80. At this university, what is the maximum number of students possible in a course that has 5 teaching assistants? (A) 130 (B) 131 (C) 132 (D) 133 (E) 134 【答案】 D 【思路】 380TS?, T=5代入 4003S,S so, the maximum number of students possible in the course that has 5 teaching assistants=133 33. 4484!item!187。s gross profit from the purchase and the sale of the desk? (A) $40 (B) $60 (C) $80 (D) $90 (E) $100 【答案】 E 【思路】 selling price=the purchase price+ 40%selling price selling price =150+ selling price selling price=150 selling price=250, the gross profit=250150=100 31. 4014!item!187。058amp。058amp。003282 26. 3282!item!187。003069 [?] For the 5 days shown in the graph, how many kilowatthours greater was the median daily electricity use than the average (arithmetic mean) daily electricity use? (A) 1 (B) 2 (C) 3 (D) 4 (E) 5 24. 3022!item!187。002849 If a = 1 and b = 2, then (2a^2 + b)(x + y) + (a + b)(x y) = (A) 0 (B) 2x (C) y x (D) x y (E) x + y 【答案】 C 【思路】 ? ?2( 2 ) ( ) ( ) ( )2 1 ( 2) ( ) (1 2) ( )0 ( 1 ) ( )a b x y a b x yx y x yxyyx? ? ? ? ?? ? ? ? ? ? ? ?? ? ? ??? 22. 2710!item!187。002761 For a finite sequence of nonzero numbers, the number of variations in sign is defined as the number of pairs of consecutive terms of the sequence for which the product of the two consecutive terms is negative. What is the number of variations in sign for the sequence 1, 3, 2, 5, 4, 6 ? (A) One (B) Two (C) Three (D) Four (E) Five 【答案】 C 【思路】題目 What is the number of variations in sign for the sequence,所以題目已經(jīng)給 sequence,不用再排序 ,variation:當下個一數(shù)字正負號與自己不同時 ,則算一次 故 (1,3)(3,2)(5,4),共三次 20. 2563!item!187。002635 In a certain board game, a stack of 48 cards, 8 of which represent shares of stock, are shuffled and then placed face down. If the first 2 cards selected do not represent shares of stock, what is the probability that the third card selected will represent a share of stock? (A) 1/8 (B) 1/6 (C) 1/5 (D) 3/23 (E) 4/23 18. 2417!item!187。002594 At a speed of 50 miles per hour, a certain car uses 1 gallon of gasoline every 30 miles. If the car starts with a full 12 gallon tank of gasoline and travels for 5 hours at 50 miles per hour, the amount of gasoline used would be what fraction of a full tank? (A) 3/25 (B) 11/36 (C) 7/12 (D) 2/3 (E) 25/36 16. 2206!item!187。002486 If m lies between the integers p and s on the number line shown, w