Re: [計量] 好幾題數學問題 part 2

看板GRE (GRE入學考試)作者CCWck (幹嘛要暱稱)時間16年前 (2010/03/29 10:01)推噓1(1推 0噓 0→)

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※ 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? 假設x>y x+y=t x-y=l x=(t+l) /2 : ANS: t+1/2 : 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? 售價 28 進價=28/1.4=20 換季價是進價的7折 = 14 : 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 : 3. If 10^50-74 is written as an integer in base 10 notation, what is the sum : of the digits in that integer? 10的50次方-74 9999....999926 前面共有48個9 48*9+2+6=440 : ANS: 440 : 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? 四種顏色的旗子一次可以拿三個作排列排出特定訊號 4*3*2=24 : ANS: 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? 81*10^15 大約是0.81*10^17 不過這應該是選擇題? 要看其他選項 : ANS: 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 ^^ 這...不是用猜的吧分母的有理化請配合使用 (a+b)(a-b)=a^2-b^2的公式這題上下同乘有理化因子√2-1就可以了 1/ √x*(√2 +1) = √2-1 /√x(√2 +1)(√2-1) = √2-1 /√x -- -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.109.134.47