Re: [計量] 10月數學機經的疑問

看板GRE (GRE入學考試)作者BlueKidds (追求卓越近乎苛求)時間18年前 (2007/10/26 22:31)推噓4(4推 0噓 5→)

留言9則, 4人參與討論串2/6 (看更多)

※ 引述《chengru (Eric)》之銘言： : 以下幾題數學機經讓我很困擾，請想的出來的同學幫忙解惑，謝謝！ : 1. 2^(x-y) = 1/64 : Col a: x : Col b: y : Ans:? x-y=-6 : 2. A ranch has horses and ponies. Five-sixths of the ponies have horseshoes. : Half of the ponies with horseshoes are Icelandic. If there are three : more horses than ponies, what is the : minimum number of horses and ponies on the ranch? : A) 12 : B) 15 : C) 27 : D) 48 : E) 54 : Ans: C （我覺得題目給的條件不夠充分，所以算不出來??） ponies是小馬，小馬沒有半隻的，所以一定要是六的倍數，而且還要是12的倍數 (因為5/6*(1/2)也要是整數) 故小馬最少要12隻，大馬要15隻 : 3. A group of 4 pumps are filling a tank. Each of the 3 smaller pumps works : at 2/3rds the rate of the largest pump. If all 4 pumps work at the same time : , they should fill the tank in what fraction of the time that : it would have taken the largest pump if it operated alone? : A) 4/7 : B) 1/3 : C) 2/3 : D) 3/4 : E) 4/3 : Ans: C （我覺得是B）速率*時間=容量假設大幫浦需要T時間，速率為V，花的時間為t，tank容量為L (2/3V)*3t+Vt=L=V*T 3Vt=VT, t=(1/3)T I think you are right : 4. Given Principal amount P,rate of interest was r ,and the amount increase : from 1990 to 1995 and 1995 to 2000 each time by r%. so the total amount was : (7/5)p at the end of 2 yrs . : Col A : r : Col B: 20 : Ans:B （我覺得題目給的條件不夠充分，所以算不出來??） : 5. Which one is larger? : Col A --- prime numbers between 2321 to 3213 : Col B--- prime numbers between 2325 to 3221 : Ans: B (No idea how this answer comes up) 2321, 2322, 2323 , 2324, none of them are prime 3214~3216, "3217", 3218~3220, "3221", 3217 and 3221 may seems like a prime 3221= 56.x^2, 故兩數可以用以下質數測試即可， 7, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53 不過至少還算的出來....等等在想想有沒有更快的方法 : 6. How much interest would accrue over a $4000 loan over 3 months at 8% : annual Simple Interest? : A)$48 : B)$96 : C)$240 : D)$320 : E)$80 : Ans: A (我覺得是E) 年利率8%, 單利，故月利率=8/12，三個月 = 2% 4000*0.02=80，I agree with you : 7. Some two huge number 78678 * 669066 : what is the sum of the digits in the units and tenth place : a) 12 : b) 8 : c) 10 : d) 6 : e) 4 : Ans:C （這題我是硬算的，有比較快的方法嗎？）這題之前有人問過，最快就是78*66=48, 4+8 =12 理由(78600+78)*(66900+66)=的答案裡面，除了78*66，其他都會到百位數 : 8. 0<w<x<y<z. If (z*z)-(y*y)+(x*x)-(w*w)=40, then what is the sum of w+x+y+z? : Ans:找不到答案如果有限定整數光用1 2 3 4就爆炸了如果沒有的話，隨便用哪個小數都會是無理數，無理數相減還是無理數也得不到40這個答案 : 9. P={1.3, 0.9, 1.5, 1.1} : Q={1.3x, 0.9x, 1.5x, 1.1x} : col a: standard deviation of P : col b: standard deviation of Q : Ans:找不到答案因為乘不同數會有不一樣的結果，你不知道是乘>1的還是<1的數 : 10. A Line K passes through (3,4) and origin, line L passes through (-3,4) and : origin. Find the angle between the lines. : 1)75 : 2)80 : 3)90 : 4)100 : Ans:找不到答案角度絕對不會是整數，直接跳過 (不然就用兩線的向量去算，會發現還是算不初整數) : 11. 4^n + 4^(n+1) = 5/64 what is n^2 . : a) 36 : b) 25 : c) 16 : d) 9 : e) 4 : Ans: d (我算不出這個答案) n=-3 沒錯阿 : 12. Given X^-1=2/y^2+1 : col a : x : col b : y^2/2 : Ans: A (我算不出這個答案) 兩數M-N>0, 倒數應該是1/N > 1/M : 13. A parabola was draw and a point on it was given as P(2,K)and it was cuting : the Y axis at a point below 2 .ie. it was open upwards the distance was asked : between th point P and the point where the parabola cuts th y axis. : a:3 : b:7 : c:2sqroot(5) : d:2sqroot(7) : e:3sqroot(3) : Ans:找不到答案 : 14. What is the probability for particular year between 1987 and 1992 to have : 53 Sunday? : Ans. 2/7 (我算不出這個答案) : 15. Given dat x*=(x-1)/x condition is x<0 not necessary find which of : the following is true? : a)2x*=2(x*) : b)-x*=x* : c)(x-1)*/x=x*... : d)(x*)*=x : Ans:找不到答案累了，剩下13~15交給下一位好了.....抱歉 -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 203.70.188.243 ※ 編輯: BlueKidds 來自: 203.70.188.243 (10/26 22:33)