Tanya prepared 4 different letters to be sent to 4 different addresses. For each letter, she prepared an envelope with its correct address. If the 4 letters are to be put into the 4 envelopes at random, what is the probability that only 1 letter will be put into the envelope with its correct address? (A)1/24 (B) 1/8 (C) 1/4 (D) 1/3 (E)3/8
选D 求过程 
One kilogram of a certain coffee blend consists of x kilogram of type I coffee and y kilogram of type II coffee. The cost of the blend is C dollars per kilogram, where C = 6.5x + 8.5y. Is x < 0.8 ? (1) y > 0.15
(2) C 大于等于7.3
这题选B。。。。怎么感觉答案是错的。。。
For any positive integer n, the length of n is defined as the number of prime factors whose product is n. For example, the length of 75 is 3, since 75 = 3*5*5. How many two-digit positive integers have length 6? (A) None (B) One (C) Two (D) Three
(E) Four
这题选C。。 一直都是记答案，却不知道算的过程
Is the integer n odd? (1) n is divisible by 3.
(2) 2n is divisible by twice as many positive integers as n.
这题选B 条件2 怎么理解呢？ 谢谢
The figure shown represents a board with four rows of pegs, and at the bottom of the board are four cells numbered 1 to 4. Whenever the ball shown passes through the opening between two adjacent pegs in the same row, it will hit the peg directly beneath the opening. The ball then has probability of passing through the opening immediately to the left of that peg and probability of passing through the opening immediately to the right. What is the probability that when the ball passes through the first two pegs at the top it will end up in cell 2? (A) 1/16 (B) 1/8 (C) 1/4 (D) 3/8
(E) 1/2
这题选D
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发表于 2017-10-29 22:01:32
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