xdf-ds-18,19 请教几道题的答案

baby11

8. If x, y, p, and q are positive, is x ≥ y ?

‍(1) px/qy=p/q

‍(2) xy = p

the answer is a, a只能推出x=y, 这也算推出来吗?

19. The table above shows the morning schedule for train X. If Juan took train X on Monday morning, did he arrive at station T on schedule?

(1) Juan arrived at station T on Monday morning 1 hour and 2 minutes after he left station S.

(2) Juan arrived at his office at 8:30 (EST) on Monday morning, which was 20 minutes after he arrived at station T.

the answer is b, i think it is d

2. The price of a television set was reduced by 25 percent. What was its original price?

(1) The reduced price was $187.50.

(2) The original price exceeded the reduced price by more than $60.00.

the answer is a, i think it is D

图片贴不上，麻烦到源文件里看一下 ds19

9. The figure above shows the present position on a radar screen of a sweeping beam that is rotating at a constant rate in a clockwise direction. In which of the four quadrants will the beam lie 30 seconds from now ?

‍(1) In each 30-second period, the beam sweeps through 3.690°

‍(2) r = 40

The answer is a, i think it is c, 不确定sweeping beam 的位置，算不出结果呀？

17. If n=p/q where p and q are nonzero integers, is n an integer ?

(1) n^2 is an integer.

(2) (2n+4)/2 is an integer.

the answer is b, i think it is d

请帮忙看一下错在什么地方了

hdrtrw112

17, n = p / q, p and q are nonzero integers, is n an integer?

1) n^2 is an integer, since n = p / q, then n^2 = p^2 / q^2 and n^2 is an integer, thus n is an integer; because if p / q is not an integer, then p / q * p / q woud not be one as well

2) (2n + 4) / 2 is an integer => n + 2 is an integer => n is an integer

thus the answer is D

teyvhf

17. If n=p/q where p and q are nonzero integers, is n an integer ?

(1) n^2 is an integer.

(2) (2n+4)/2 is an integer.

17.答案是对的，B。

条件1不对。比如：n^2=81/3=27是整数，但是n=9/根号下3 不是整数

17题有严重疑问：n=9/根号下3 不是整数，n的表达式是n=p/q where p and q are nonzero integers,所以n不能等于9/根号下3

迷惑

himba

8. A可以得到x=y,而题目是要求满足x>=y,条件1和条件2联立也得不到。我也觉得应该选E。

19. 没图.

2. A。条件2不对。

(2) The original price exceeded the reduced price by more than $60.00.

说的是more than,呵呵，要看清楚。

9. 没图

17. 答案是对的，B。

条件1不对。比如：n^2=81/3=27是整数，但是n=9/根号下3 不是整数。