Re: [計量] 最後幾題計量問題?

看板GRE (GRE入學考試)作者cassine (　)時間16年前 (2010/04/09 15:22)推噓0(0推 0噓 0→)

留言0則, 0人參與討論串2/2 (看更多)

※ 引述《abc03301016 (123)》之銘言： : Q1. A certain characteristic in a large population has a : distribution that is symmetric about the mean m.If 68 percent : of the distribution lies within one standard deviation d of the mean : , what percent of the distribution is less than m + d? : A. 16% : B. 32% : C. 48% : D. 84% : E. 92% 某個大量的人口分布對稱於平均值，如果平均值正負一個標準差裡面有 68%的人，問落在小於 m + d區間的有多少？正負一個標準差裡面有 68%，代表正負一個標準差以外有 32%，由於左右對稱，因此大於平均值加一個標準差的有 16%，故小於平均值加一個標準差的有 84%，選D) : Q2. A seller marks the price of an article 35% more of the wholesale : price and he offers some discount. If he wish to get a profit : of 21.5%. What is the percentage difference between marked : price and selling price? : A. 12.5 : B. 10 : C. 25 : D. 22.5 : E. 15 某物品的單買價格比整體購買平均價格貴了 35%，然而實際售價又給了折扣，如果商人希望維持 21.5%的利潤，那標價和實際售價間有多少 %的差異？原價 1、標價1.35、售價 1.35x = 1.215，故 x = 0.9 題目應該是以標價為基準，故選B) : Q3. John traveled 80% of the way from Yellow-town to Green-fields : by train at an average speed of 80 miles per hour. The rest of the : way John traveled by car at an average speed of v miles per hour. : If the average speed for the entire trip was 60 miles per hour, : what is v in miles per hour? : (a) 30 : (b) 40 : (c) 50 : (d) 55 : (e) 70 不妨假設兩地距離100 miles，前面80 miles是以時速80英里前進，所以花了 1小時剩下20英里以 v的速度前進，最終平均速度是每小時60英里。總共旅行時間是 100/60 = 5/3 小時，開車的時間是 2/3小時，因此開車的平均速度是 20/(2/3) = 30，選A) : Q4.Two cylindrical containers are given with circular base : area of 4Pie and 8Pie. 4PI container is filled with a : liquid to 3'' height and the 8Pie container to 1" height. : The liquid from 4Pie container is pored into the 8Pei : container till the level of liquid in both of them is equal. : Find the final height : of the liquid? : Ans: 5/3 兩個圓柱形的罐子底面積分別為4pi和8pi，4pi那個裝水到三吋的高度，而8pi則裝到一吋高度，然後把4pi罐子裡面的水往8pi那個罐子裡面倒，高度一樣時的高度為何。總共有12pi*inch + 8pi*inch的水，總體底面積是12pi，因此平均高度就是 20/12 = 5/3吋。 : Q5. Roger sold a watch at a profit of 10%. : If he had bought it at 10% less and sold it for $13 less : he would have made a profit of 15%. : What is the cost price of the watch? : A) $220 : B) $300 : C) $400 : D) $480 : E) $540 : Ans: A 假設原來的購買價是 x，則售價是1.1x 如果購買價格便宜10%，賣出售價又少13元的話，獲利有15%，問購買價。 (1.1x - 13)/0.9x = 1.15 答案應該是 200元才是。 : Q6.A car goes around a circle of radius of 14km, in the first : round it travels with a speed of 11km/hr, in sub sequent : rounds its speed increases by 11km/hr in each round. : how much time does the car take to cover a dist of 440km : a)14*8/5 b)15*14/18 c)18*4/15 d)4*15/18 e)7*4/15 : Ans: C 半徑14公里的圓形跑道，車子初速度是11km/h，每跑完一圈加速11km/h，問總里程累積超過 440公里時，要花多久時間？第一圈花費時間2*14*pi/11 = 8小時（用到 pi ~ 22/7的近似），440公里總共是 440/(2*14*pi) = 5圈。第 n圈速度 n倍，因此繞行時間為 1/n。因此花費時間就是 8 + 8/2 + 8/3 + 8/4 + 8/5 = 274/15小時。 C)的答案應該是帶分數形式 18+4/15才對 : Q7. Three quarts of a bleaching chemical, minmum, : contains 5% hydrogen peroxide and water. : A different type of bleaching chemical, maxim, : which contains 20% hydrogen peroxide, will be mixed : with the three quarts of minum. : How much of type maxim should be added to the 3 quarts of minum : so that the resulting mixture contains 15% hydrogen peroxide? : A. 3 quarts : B. 3.75 quarts : C. 4.5 quarts : D. 6 quarts : E. 9 quarts 答案D)，用比例去算計就好。 : Q8. A tank contains 10,000 gallons of a solution that is 5 percent : sodium chloride by volume. If 2,500 gallons of water evaporate from : the tank, the remaining solution will be approximately what percent : sodium chloeide? : Ans: 6.67% 原來的溶質有10,000 * 5% = 500 後來的溶液有10,000 - 2,500 = 7,500，因此濃度為500/7,500 = 1/15 = 6.67% 題外化，這題在化學上單位是有問題的，重量百分濃度的定義非如此。 -- ○ ____ _ _ _ _ ____ _ _ ____ _____ ____ 。 ★(_ _)( \( )( \/ )( ___)( \( )(_ _)( _ )( _ \ ｏ _)(_ ) ( \ / )__) ) ( )( )(_)( ) / ● ‧ (____)(_)\_) \/ (____)(_)\_) (__) (_____)(_)\_) ★ ｏ -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 218.166.226.73