几道不懂的数学题,麻烦求解~

starchang14

DS

1. Town T has 20,000 residents, 60 percent of whom are female. What percent of the redisents were born in Town T?
(1) The number of female residents who were born in Town T is twice the number of male residents who wre not born in Town T.
(2) The number of female residents who were not born in Town T is twice the number of female residents who were born in Town T.

答案是B,我选的C.

我的解题丝路:
由题知,Town T里女性总数为20,000*60%=12,000. 剩下40%为男性,人数为8000.
设女的出生在T的为x,所以没出生在T的女性为1200-x. 设男的出生在T的为y,所以没出生在T的男性为8000-y.
单看(1)列出x=2(800-y),但无法解答.  单看(2)列出1200-x=2x, 解出x=400.
我觉得怎么也要借助(1)的条件,把男性在T出生的在T的人数算出来啊.才能拿出生在T的男性和女性总数除以T的总人口数.


2. On a certain day it took Bill three times as long to drive from home to work as it took Sue to drive from home to work. How many kilometers did Bill drive from home to work?
(1) Sue drove 10 km from home to work, and the ratio of distance driven from home to work time to drive from home to work was the same for Bill and Sue that day.
(2) The ratio of distance driven from home to work time to drive from home to work for Sue that day was 64 km per hour.

我看不懂条件里的 "the ratio of distance driven from home to work time to drive from home to work" 是什么意思, time是指什么啊,到底这个ratio是什么跟什么在比呢?

答案是A.



3. If positive integer x is divided by 2, the remainder is 1. What is the remainder when x is divided by 4?
(1) 31<x<35
(2) x is a multiple of 3

答案是C,我选的A.
题干说x是正整数,除2余1,由(1)得知,x就为33.   33除以4余1就求出来了.
但是答案是C,为什么要(1)+(2)一起才能求解呢?


4. Is x less than y?
(1) x-y+1<0
(2) x-y-1<0

答案是E,我选的A.


谢谢~~

zhumiao

  感觉是答案错了  - -