Re: [問題] 陳向東數學一些問題
※ 引述《GOKU123 (GOKU)》之銘言：
: p.166
: 第25題
: A rectangular floor with an area of 12 square meter is drawn to scale with 2
: centimeters representing L meter.
: QA: The area of scale drawing of the floor OB: 24 square centimeters
: Ans: (A) QA>QB
: 問題: 如果把 2 cm 縮小為 L m, 設原圖形兩邊長為x,y. 新圖型的邊長應為2x/L,2y/L
: xy=12 那面積變成4xy/L^2 = 48/L^2 那麼大小不就取決於L? 答案應該是(D)?
: p.255
: 第6題 比大小
: For the line with equation y-ax+b, ab≠0,
: the x-intercept is twice the y-intercept.
: QA:The slope of the line OB:1/2
: 答案是B
: 問題是:X截距為Y截距兩倍，斜率不是應該會有正或負?感覺斜率應該是±1/2?
截距有正有負，如果斜率為正的話，這條直線的X截距與Y截距一定是一正一負，
怎麼樣都不可能有二倍的關係！
: p.257
: 第17題
: In the xy-plane, line k is a line that does not pass through the origin.
: Which of the following statements individually provide(s) sufficient
: additional information to determine whhether the slope of line k is negative?
: Indicate all such statements.
: (A) The x-intercept of line k is twice the y-intercept of line k
: (B) The product of the x-intercept and the y-intercept of line k is positive.
: (C) Line k passes through the points(a,b) and(r,s), where(a-r)(b-s)<0
: Ans:ABC
: 問題:(A)裡面 同樣截距是兩倍，斜率應該會是有正有負吧?
理由同上！
: p.258
: 第20題
: If the total of commuters to Country W is twice the number to Country Z, and
: if the average number of vehicles that transport commuters daily to Country W
: is 30,000, what is the approximate average number of vehicles that transport
: commuters daily to Country Z?
: Ans:(A) 12,000
: 問題:本題有附圖，但我覺得題目跟圖表無關
: 算法為:total=average*days 而days為常數,
: 所以 total(W)為total(Z)的兩倍;那average(Z)就應該是average(W)的1/2
: 30000/2=15000---(B)選項 嗎?
: p.260
: 第9題
: 題目是不是沒給完整阿@@?
: p.261
: 第18題
: George earned 80,85 and 90 on the first three test in his geography class.
: Because he didn't have time to study, he decides to guess randomly on the
: final test. That test has ten true-false questions, each worth 10 points.
: What is the probability his final average is more than 85?
: (A)12/2^8 (B)11/2^8 (C) 12/1024 (D) 11/1024 (E) 0.5
: Ans:(D)
: 問題:不會算= =?
: 算法: 期末平均要 >85 代表期末考要考90或100
: 所以 要對九題以上 => C十取九 * (1/2)^9
: ....沒答案XD
: --------------------
: 感謝解答QQ
: 另外想問一下
: 1.數學做陳向東就好了嗎 還是有什麼其它適合的題目可以再練習?
: 2.一些美國常用的單位換算 feet,ounce,dime等 需要背嗎?
: 3.大家正常的話，數學應該留幾分鐘檢察?
: 4.圖表問題，因為不像書本可以用尺去對照圖表的數據，這在機考有影響嗎?
: 感激不盡!!!^^"
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