Re: [計量] 好多題計量請教

看板GRE作者wearytolove (奪真書生A.W.)時間13年前 (2011/01/13 00:29)推噓2(2推 0噓 3→)

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※ 引述《balance9235 (退伍變米蟲)》之銘言： : 1. For all real numbers, xy+x=5 and y^2+2y=19 : Column A Column B : x/y+1 1/4 ANS: C 這題不太會算暴力解:y=-1±2√5 ,所以x(y+1)=5 當y=-1+2√5 x=(√5)/2 x/y+1=(48+√5)/38 當y=-1-2√5 x=-(√5)/2 x/y+1=(48-√5)/38 應該是都比1/4大= =?還是題目或答案有錯啊.... 有括號的話請加一下.... : 2. At a congress, 50% of the congressmen are from party A, : 40% are from party B, and the remainder are from other parties. : If 80% of all the congressmen vote no on a certain issue, : What will the LEAST percent of the congressmen from party B vote no? : (A) 10% : (B) 20% : (C) 30% : (D) 40% : (E) 50% ANS:(E) 我算是80%-50%-10%=20% B黨要出B黨的20/40=50% 但我覺得這題意有夠不清 : 3. : Column A Column B : The number of ways 720 : that a bracelet may be : strung up with seven : different color beads. ANS: B 不過我用圓桌坐人法算是 C 7! /7因為可旋轉 /2因為可翻轉=360 圓桌座人不可翻轉,但手鍊可以反過來戴只是美國人有那麼聰明嗎.... : 4. In the xy-coordinate plane, the vertices of the triangle ABC are : A (15,1), B (9,3) and C (4,5). What is the slope of the altitude to side : 線段AB? : (A) -1/3 : (B) 1/3 : (C) 2/3 : (D) -3 : (E) 3 ANS (E) 我算成線段AB的斜率 AB線段斜率是△y/△x=(1-3)/(15-9)=-1/3 問的是AB上的高的斜率,與AB垂直,兩垂直線斜率交乘=-1 所以Ans=3 : 5. : Column A Column B : The percent increase of 400 : the area of a circle if : its diameter is doubled. ANS: B 打著打著突然想通了，A是增加300% : 6. If the perpendicular bisector of the segment with endpoints : A (1,2) and B (2,4) contains the point (4,C), then the value C is : (A) 7 : (B) 4 : (C) 4/7 : (D) 7/4 : (E) -4 ANS:(D) 看不懂題目有一個垂直二分切線,把AB切成兩半,這切線經過4,C 因此這個線經過AB中點=(1.5,3),斜率與AB交乘=-1,因此該線斜率=-1/2 B(2,4) 當x=4,從1.5前進2.5,則y減少5/4,變成3-5/4=7/4 / (1,2)A/＼就是這條啦 : 7. If a cube has an edgeof length 10, then the length of the segment : connecting the center of a face of the cube to any vertex not contained : in the plane of that face is : (A) √6 : (B) 6√5 : (C) 5√6 : (D) 3√5 : (E) 10√6 ANS:(C) 完全看不懂一個正方體邊長=10,則從其中一面的中點到任何一個這一面沒碰到的頂點的距離為何？ (一個正方體有8個頂點,任何一面會包含4個) 一面中點到一面頂點距離=10√2/2=5√2,用畢氏定理可得答案=√(10^2+(5√2)^2) =√150=5√6 : 8. After the first term, rach term in a sequence is 3 greater than 1/3 of : the preceding term. If t is the first term of the sequence and t≠0, : what is the ratio of the second term to the first term? : (A) t+9/3 : (B) t+3/3 : (C) t+9/3t ANS:(C) : (D) t+3/3t 題目意思是不是第一項的三分之一加三等於第二項，我怎麼算(A) : (E) 9-2t/3 m1=t m2=t/3+3 m2/m1=(t/3+3)/t=(t+9)/3t : 9. For all positive numbers, x-7, x, and x+1 are the lengths of sides of a : right triangle. : Column A Column B : x 12 ANS: 我用畢氏定理算出來不是有理數 X^2+2X+1=X^2+X^2-14X+49 X^2-16X+48=0 (X-12)(X-4)=0 又三角形邊長為正數,x-7>0 4不合,因此x=12 : 10. If the sum of the two numbers is 21, and the difference of their square : is 63, what is the greater of the two numbers? : (A) 8 : (B) 9 : (C) 10 : (D) 11 : (E) 12 ANS:(E) 最後一句不太懂兩數相加=21,平方相減=63,大的那個是啥 x+y=21 x^2-y^2=63 x=12 y=9 因此大的是12=(E) : 11. Of the 120 people in a room, 3/5 are women, and 2/3 are married. : Column A Column B : The maximum number of : women in the room who 72 ANS: B 我算 C : could be married. 女人的數量72，結婚的數量80，最多72人其實結婚不限性別啊...(題外話) 120*3/5=72是女人 120*2/3=80人結婚所以應該是C沒錯吧 : 12. Three friends are playing a game in which each person simultaneously : displays one of three hand signs:剪刀、石頭、布. How many different : combinations of the signs are possible? : (A) 7 : (B) 9 : (C) 10 : (D) 12 : (E) 27 ANS:(C) 想不出來第十種組合是甚麼.... 三人相同=3 兩同一不同=6 三人都不同=1 相加=10 : 13. A 1,000 bonus is to be divided among three people so that Jane receives : twice as much as Robert, who receives 1/5 as much as Wendy. How much : money should Wendy receive? : (A) 100 : (B) 125 : (C) 250 : (D) 375 : (E) 625 ANS:(E) 誰是誰的幾倍一直搞不清楚 Jane=2*Robert Robert=1/5*Wendy ,所以Jane=2/5*Wendy 8/5*Wendy=1000 Wendy=125*5=625 : 14. : Column A Column B : The number of pounds : of chocolate that can 5 : be purchased for 12USD : if 4.5 pounds of : chocolate cost 10USD. ANS: A 題目看不懂假如4.5鎊要10元,12元可以買幾鎊=12/10*4.5=5.4>5 : 15. The sum of the digits of a three-digit number is 16. The tens digit of : the number is 3 times the unit digit, which is 1/4 of the hundreds digit. : Column A Column B : The three-digit number 800 ANS: A 跟13.題一樣的問題三位數的數字相加=16 十位數是個位數的3倍個位數是百位數的1/4 所以個位數=1,則數字=431 個位數=2 數字為862>800 A -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 111.70.212.167

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