Re: [計量] 10/13~10/18 印度數學問題

看板GRE (GRE入學考試)作者nehsband (bibo)時間15年前 (2010/10/23 10:21)推噓1(1推 0噓 1→)

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※ 引述《calka (^^)》之銘言： : 這些是我不會的數學，麻煩大家了，謝謝~~~ : 10/13印度數學 : http://www.drrajus.com/forum/viewtopic.php?t=7893 : 1. If a number is 20% more than x and is equal to the number which is 10% less than y, then what is the increase in y with x? let z=1.2x x=5/6z then y/x=4/3 y=4/3x y=0.9x y=10/9z : 3. Col A: Mean of all the numbers from 1 to 31 inclusive : Col B: some value (xxx) : 這題我看大家求colA的答案就跟我不一樣...我算出16 31 numbers(odd) then mean value is (1+31)/2=16 : 5. Col A: The remainder of 10^22+1 when divided by 11 : Col B: 2 : 這題我看很多回報的都說是2 我已經看到背起來答案了 : 但是考試的時候這題真的要算的話，是要怎麼算...真的10的22次方去算嗎? : 因為我只有背到10的10次方是1024... example: 100/11=9...1 10000/11=909...1 1000000/11=90909...1 then we can tell the remainder of 10^22 would be also one therefore, 1+1=2 : 9. Given two groups ‘G’ and ‘H’. If 30% of number of items in G and 20% of number of items in H are common, then : Col A: Number of items in G : Col B: Number of items in H : 答案有寫B或是D，不曉得是哪個對...我是B的 common: 共有的??(I have no idea, sorry) G:x number of items H:y number of items 0.3x and 0.2y are common, I don't know which one(x or y) is bigger. : 10. Given two points on the circumference of the circle of centre ‘O’ as P(10, -2) and Q(22, -2). If the angle POQ is 120°, find the circumference of circle? : 這題我算不出來 distance between P and Q is sqrt{[(22-10)^2+0^2]}=12 draw a line from the center O to the side of the circle,create a bisect angle, name the point as "R" then the angle of POR is 60 degrees and let the distance OP, is also a radius,(r). r sin60= 12/2=6 r=4sqrt3 circumference is 2r pi =8pi sqrt3 : 11.(有圖)Given a figure like above. If the side length of the square is 4, then find the area of the shaded region? : 答案是8pi-1,不曉得怎麼算的.... small circle radius= 2 calculate one fourth of the area first... big circle radius= 4 1/4 pi 4^2 -1/4 pi 2^2 2 - 2^2= 2pi-4 (big circle) (small circle) (square) the area is 4(2pi-4)= 8pi-16 : 12. (有圖)Given a figure of two concentric circles like above and the radius of bigger circle is twice the radius of smaller circle. If a point ‘p’ lies in the circle, then : Col A: The probability of the point being in the shaded region : Col B: 3/4 : 也不知道怎麼算... let the radius of big circle: 2r the radius of small circle: r probability=pi[(2r)^2-r^2]/pi(2r)^2=3/4 The answers are just for reference.(some may be wrong) I will try my best to answer the rest of the questions as soon as possible. -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.112.244.190 ※ 編輯: nehsband 來自: 140.112.244.190 (10/23 10:23) ※ 編輯: nehsband 來自: 140.112.244.190 (10/23 10:25)