1, If n and y are positive integers and 450y=n^3, which of the following must be an integer? 1) y / (3* 2^2 *5) 2) y / (3^2 *2*5) 3)y / (3*2* 5^2) A, None B, 1 only C, 2 only D, 3 only E, 1,2 and 3 PREP上的题, 我选E, 答案选B. 请教~~~ 2, At a dinner party, 5 people are to be seated aroung a circular table, two seating arrangements are considered different only when the positions of the people are defferent relative to each other. What is total number of different possible seating arrangements for the group? A, 5 B, 10 C, 24 D,32 E,120 也是PREP上的题, 答案选C, 如何解? |