Re: [計量] 好幾題數學問題 part 2

看板GRE作者Maccer (把給壓羅)時間16年前 (2010/03/29 10:32)推噓3(3推 0噓 1→)

留言4則, 3人參與討論串4/4 (看更多)

※ 引述《Despond (<(￣︶￣)/)》之銘言： : 這次的問題是我有的題目我根本不了解問什麼囧" : 再度麻煩版友 @@ : ============================================================================== : 1. The sum of two numbers that differ by 1 is t. In terms of t, what is the : value of the greather of the two numbers? : ANS: t+1/2 設兩數為 A和B _ A+B=t / \_ A-B=1 解聯立 2A=t+1, A=t+1/2, then B=t-1/2, so A>B : 2. A store charges $28 for a certain type of sweater. This price is 40 percent : more than the amount it costs the store to buy one of these sweaters. At an : end-of-season sale, store employee can purchase any remaining sweater at 30 : percent off the store's cost. How much would it cost an employee to : perchase a sweater of this type at this sale? : ANS: $14.00 我不了解這題目的意思百分之四十那部分我不懂題目表是的意思 $28這個價錢比成本多了百分之四十所以設成本為x, x*(1+0.4)=28, x=20 然後他說過季商品店員只需花成本的七折就可以買到剩下的過季商品所以就是20*0.7=14 即為所求!! : 4. 看不懂題目的意思 : Each signal that a certain ship can make is composed of 3 different flags : hanging vertically in a particular order. How many unique signals can be : made by using 4 different flags? : ANS: 24 題目是說一艘船所產生的訊號是由三種不同旗子所排列而成的現在問你利用四種不同的旗子可以創造出幾種不同的訊號一個訊號由三種不同旗子組成所以第一個旗子我們有四種選擇 4 * 第二個旗子我們剩下三種選擇 3 * 弟三個旗子我們只剩兩種可以選擇 2 ------------------------------------------ = 24 : 5.這題我想問有沒有比較快速的方法或是絕竅 : The value of (9 x 10^7)(9 x 10^8) is closest to which of the following? : ANS: 10^17 10^7*10^8=10^15 (相乘指數相加) and 9*9=81 is closest to 10^2 then again 10^2*10^15=10^17 : 6. If x > 0, then 1/ (√2x +√x) = : ANS: √2-1 / √X 這類型題目相當不擅長,請問這要怎麼改進 @@ 幾乎每次都會算錯 : 再次謝謝各位版友 ^^ 有理化上下同乘(√2x -√x)=> (√2x -√x)/ 2x-x= (√2x -√x)/x 分子提出√x=> √x(√2-1)/x, 又x= √x*√x 所以上下同時約分√x, 即為所求(√2-1)/√x -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 220.135.131.46

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Despond

03/29 12:25, , 1^F

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OalexO

03/30 00:37, , 2^F

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louis925

03/30 03:11, , 3^F

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