Re: [計量] 請問三題數學

看板GRE (GRE入學考試)作者sovereignty (One goal.)時間17年前 (2008/08/11 12:00)推噓1(1推 0噓 0→)

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※ 引述《toughbank (JakeHsu)》之銘言： : 1. : m^2+n^2=7 : ColumnA ColumnB : _______ _______ : m+n 5 答案:D 沒給限制 (如 m, n 要整數)，所以 m^2 + n^2 = 7 有無限多組解。故無法比較。 : 2.If a motorist had driven 1 hour longer on a certain day : and at average rate of 5 miles per hour faster, he would have : covered 70 more miles than he actually did. How many more : miles would he have covered than he actually did if he had : driven 2 hours longer and at an average rate of 10 miles per : hour faster on that day? : ans:150 Distance = Velocity * Time D0 = 原始位移；V0 = 原始速度；T0 = 原始時間。 D0 = V0 * T0 ...... (1) D0 + 70 = (V0 + 5) * (T0 + 1) ...... (2) 由 (1) (2) 可得 5T0 + V0 = 65 ...... (3) 設 x 為所求 D0 + x = (V0 + 10) * (T0 + 2) ...... (4) 代入 (3)，可得 x = 150 # : 3.Solution Y is 30 percent liqid X and 70 percent water. If : 2 kilograms of water evaporate from 8 kilograms of solution Y : and 2 kilograms of solution Y are added to the remaining 6 : kilograms of liquid, what percent of this new solution is liquid X? : ans:37.5% 溶質重溶質重溶液的重量百分比濃度 = ---------- = --------------- 溶液重溶質重 + 水重 30 Y 的重量百分比濃度 = ------- = 0.3 = 30% 30 + 70 原來溶質重新增溶質重 8 * 0.3 + 2 * 0.3 3 ^^^^^^^ ^^^^^^^ 新溶液 (X) 重量百分比濃度 = -------------------- = ----- = 37.5 % 8 - 2 + 2 8 ^^^ ^^^ 減掉水重加入溶液重 : 請好心人解釋一下.. 全都是台灣的國中數學程度，GRE 的 Verbal 考台灣的研究所以上程度， Quantitative 卻只考國中程度，天差地遠！ -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.112.21.151 ※ 編輯: sovereignty 來自: 140.112.21.151 (08/11 12:02)