GMAT数学题 急求牛人解答 感激不尽： Q4 How many seconds will it take for a car that is traveling at

请问谁能讲一下为什么

How many seconds will it take for a car that is traveling
at a constant rate of 45 miles per hour to travel a
distance of 220 yards? (1 mile=1,760 yards)

A. 8
B. 9
C. 10
Answer C
Q5
If x^3y^4=5,000, is y=5?
(1)y is a positive integer.
(2)x is an integer.
____________________________________________________________
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.
Answer: C
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第一题
一个汽车以45英里每小时的速度匀速行驶，（1英里等于1760码），问行驶220码需要多少秒？
答案：220*3600/(45*1760) =10

Q5
考察命题充分必要条件的
选项意思分别是： （1）命题单独充分，（2）单独不充分；
（2）命题单独充分，（1）单独不充分；
（1）（2）命题联合起来充分，单独都不充分。
充分的意思就是能否得出：if的结论。
显然只有C满足题意，此时我们可以得出x=2,y=5

A,2，C

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