|
Q2: A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any 1 of the 3 cars each time that passenger rides the roller coaster. If a certain passenger is to ride the roller coaster 3 times, what is the probability that the passenger will ride in each of the 3 cars? A. 0 B. 1/9 C. 2/9 D. 1/3 E. 1 Answer: 首先,你要知道这道题的答案需要把每一辆车被选择一次的概率相乘.那么第一辆车可任选即概率为1,第二次在三辆车中选另两辆未被选过的车中的一辆的概率为2/3,最后一次在三辆车中选唯一一辆未被选过的车的概率为1/3: 1*2/3*1/3=2/9 这题是搜索到NN的解释,看不懂?请再明示一下吧. Q5: Is x > k? (1)
2x • 2k = 4 (2)
9x • 3k = 81 A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient. B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient. C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient. D. EACH statement ALONE is sufficient. E. Statements (1) and (2) TOGETHER are NOT sufficient. 答案是E,我觉得是C,主要是我数学太差了,所以提上来再问问大家. Q9: A gardener is going to plant 2 red rosebushes and 2 white rosebushes. If the gardener is to select each of the bushes at random, one at a time, and plant them in a row, what is the probability that the 2 rosebushes in the middle of the row will be the red rosebushes? A. 1/12 B. 1/6 C. 1/5 D. 1/3 E. 1/2 to Q9. 4 rosebushes, so the total possibility is Permutation(4,4), ie, there are 24 possible outcomes to order the place of them, then for the red rosebushes in the middle, there are two outcomes as r1 r2 or r2 r1 in the middel of the place, and for the white ones, there are two outcomes as well, ie, w1 r r w2, w2 r r w1 , so the numerator should be 2*2, and denominator should be 24. 4/24=1/6 看了解释,更不明白了.请问有更合适我这种程度的做法吗? 11.In a corporation, 50 percent of the male employees and 40 percent of the female employees are at least 35 years old. If 42 percent of all the employees are at least 35 years old, what fraction of the employees in the corporation are females? A. 3/5 B. 2/3 C. 3/4 D. 4/5 E. 5/6 我的做法是设总员工为100人, 那么女员工占总人数的比例是:40/100=2/5,答案是D,不知道怎么算了. 我的做法是设总员工为100人, 那么女员工占总人数的比例是:40/100=2/5,答案是D,不知道怎么算了.Q14: If 1050 – 74 is written as an integer in base 10 notation(以10为底数), what is the sum of the digits in that integer? A. 424 B. 433 C. 440 D. 449 E. 467 10^50=10000000....00000(50个0) 10^50-74=9999999...99926(50-2个9) 所以sum=48*9+2+6=440 (x+5+2x)^2 - (x+5)^2 = 132 => x=3, 这是某一题的解题步骤,我把它分解成8X^2+20X-132=0,就怎么也算不下去了, 132的因子好像没有相加等于20的呀. Q20: If x > 0, then 1/[√(2x)+√x] = A. 1/√(3x) B. 1/[2√(2x)] C. 1/(x√2) D. (√2-1)/√x E. (1+√2)/√x √(2x)-√x/(√(2x)+√x)(√(2x)-√x) ＝(√(2x)-√x)/x 分式上下同除√x)，得 (√2-1)/√x √(2x)-√x/(√(2x)+√x)(√(2x)-√x)---√(2x)-√x/X,但怎么也求不出等于(√2-1)/√x. 不知道哪步出错了!!~~?? Q22: In the sequence 1, 2, 4, 8, 16, 32, …, each term after the first is twice the previous term. What is the sum of the 16th, 17th, and 18th terms in the sequence? A. 218 B. 3(217) C. 7(216) D. 3(216) E. 7(215) 没有搜索到讨论,不知道怎么思路?? Q23: In the xy-plane, point (r, s) lies on a circle with center at the origin. What is the value of r2 + s2? (1)
The circle has radius 2. (2)
The point (√2, -√2) lies on the circle. A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient. B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient. C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient. D. EACH statement ALONE is sufficient. E. Statements (1) and (2) TOGETHER are NOT sufficient. 也是没有思路,更没有搜索到讨论贴??!! Q25: A photographer
will arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row. The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her. How many such arrangements of the 6 people are possible? A. 5 B. 6 C. 9 D. 24 E. 36 我搜索到的讨论都是土算算出来的,我可土算只能算出4种排列.请教有啥科学算法不? Q28: For any positive integer n, the sum of the first n positive integers equals [n(n+1)]/2. What is the sum of all the even integers between 99 and 301? A. 10,100 B. 20,200 C. 22,650 D. 40,200 E. 45,150 （（（301-99）/2）*（301+99））/2=20200 如果按以上算法(我搜索来的), 题目中的条件[n(n+1)]/2还有什么用呢? 而且这个算法俺想不明白思路. 31.A positive integer n is said to be “prime-saturated” if the product of all the different positive prime factors of n is less than the square root of n. What is the greatest two-digit prime-saturated integer? A. 99 B. 98 C. 97 D. 96 E. 95 这题是指:5个答案中哪个数的所有质因子之积小于这个数的平方根? 我是把答案带入算的, 还有科学方法不? Q34: The function f is defined by f(x) = - 1/x for all nonzero numbers x. If f(a) = - 1/2 and f(ab) = 1/6, then b = A. 3 B. 1/3 C. - 1/3 D. -3 E. –12 答案是:1/3; 可我指的是-3, 这是怎么算出1/3的呢? Q36: Each signal that a certain ship can make is comprised of 3 different flags hanging vertically in a particular order. How many unique signals can be made by using 4 different flags? A. 10 B. 12 C. 20 D. 24 E. 36 要考虑不同的排列顺序，所以是A(3,4)=24----不理解这位NN的解释?
Q37: A jar contains 16 marbles, of which 4 are red, 3 are blue, and the rest are yellow. If 2 marbles are to be selected at random from the jar, one at a time without being replaced, what is the probability that the first marble selected will be red and the second marble selected will be blue? A. 3/64 B. 1/20 C. 1/16 D. 1/12 E. 1/8 分2次取,把2次的概率相乘。第一次从16中取一个红的：C(4,1)/C(16,1),第二次从15中取一个蓝的：C(3,1)/C(15,1) 我不懂为什么要用 红)---4个里取1个除以16里取1呢? 就是除法在概率题里用在什么情况下呢? 我的问题太多了, 身边人都懒得教我(嘻嘻,都是牛人F1们,我的数学题对他们来说太易了),我是实在不好意思了,老来麻烦大家. 我的OG看完概念了,在补充看陈向东,可一遇到实题就傻了.笨笨笨的乌,可我也想飞.... 再次感谢大家!!! |
京公网安备11010202008513号 京ICP证101109号 京ICP备12012021号
发表于 2007-5-19 11:59:00
楼主
