60.DS, 不放回抽样,共有English and Spanish 良种,抽两本,问抽得at least one english book的概率。 1)english 与spanish 的比是1:3 2)书的总数少于20本
61.scientist studies the migration trend of a group of geese. The group contains 30% male geese. Among the geese that later on migrated, 20% are male. What is the ratio of migration factor for male geese to the migration facotr for female geese? (migration factor for sex X = number of migrated individual with sex X/total number of individuals with sex X) Solution: Assume total geese X, of which Y migrated. The answer is simple [(20%Y)/(30%X)]/[(80%Y)/(70%X)] = ...
62.Some guy has 6 albums of anthology from which he read one poem at least. All peoms in the albums are different. Did he read more than 6 poems from at least one of the album? a) he has read 22 poems in total. b) the numbers of poems he read from each album are all distinct. Anwser: C
63. k, l, m are positive integers, does k has more prime factors than m a) k = 30l b) m = 10^k Answer: C
64.sqrt{2sqrt(63) 2/[8 3sqrt(7)]} Answer: 4
65.two right cylinders, A and B. radius of A is 2 times radius of B. height of A is half the height of B. If B s radius is x and B s height is y. What is the difference between surface area of A and that of B. Solution: A s suface 2*pi*(2x)^2*(y/2) pi*2*(2x)*(y/2) B s surface 2*pi*x^2*y pi*2xy Difference = A s - B s