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标题: 请教一道DS [打印本页]

作者: joywzy 时间: 2003-1-18 16:04 标题: 请教一道DS

25. A total of 774 doctorates in mathematics were granted to United States citizens by American universities in the 1972-1973 school year, and W of these doctorates were granted to women. The total of such doctorates in the 1986-1987 school year was 362, and w of these were granted to women. If the number of doctorates in mathematics granted to female citizens of the United States by American universities decreased from the 1972-1973 school year to the 1986-1987 school year, was the decrease less than 10 percent?
(1)1/10< W/774 < 1/9
(2)W=w+5

Ans; C

请教解题思路
另外，less than 10 percent?是什么的percent
是否：W/774- w/362 是否等于10percent?

作者: mayfly 时间: 2003-1-19 17:36

Agree with C, Ask (W-w)/W From 1) 77.4 作者: joywzy 时间: 2003-1-19 20:19 标题: to maryfly

Thank u for your response.

做DS时，我经常对*percent 感到迷惑。因为我搞不懂是什么的percent.怎样确实是什么的percent. 不知有什么办法没有？

作者: lisaislisa 时间: 2003-1-19 20:34

less than 10 percent?是什么的percent
------------------------------------
is the percent decrease
that is (W-w)/W*100%

作者: mayfly 时间: 2003-1-19 20:34

用中文想想谁比谁多或者少，比前面是差，比后面的就是分母！

作者: lisaislisa 时间: 2003-1-19 20:37

en...
W-w is the amount decreas
divide W then we get the percentage

to get more informative answers pls consult og. math review P37

^^

作者: joywzy 时间: 2003-1-19 20:51 标题: 以此题为例

分子是the number decreased from the 1972-1973 school year to the 1986-1987 school year;分母是from the 1972-1973 school year ，对吗？

另外，我找OG MATH REVIEW P37找不到相关解释。

再举下一题为例：
13. Did the population of Country S increase by less than 20 percent from 1965 to 1975 ?

(1) The population of Country S in 1965 was 180 million.
(2) The population of Country S in 1975 was 1.17 times what it was in 1965.
Ａns: B
(2) set the population of Coutry S in 1975 as X, set the population of Country S in 1965 as Y
idea shall be as follow:
(X-Y)/X
and (2)=> X=1.17Y 代入，得出结论
因此分母应是两个概念（１９６５，１９７５）中的前一个对吗？

作者: lisaislisa 时间: 2003-1-19 21:02

right
here is from og

percent exchange
Often a problem will ask for the percent increase or decrease from on quantity to another , eg, if the price of an item increases from $24 to $30 what is the percent increase in price ? To find the percent increase , first find the amount of the increase then divide this increase by the original amount , and expreess this quotient as a percent In the eg , the percnet increase is 30-24 therefore the percent increase is 6/24=25%

Likewise , to find the percent decrease eg the price of an item is reduced from $30 to $24 first find the amount of the decrease then divide this decrease by the original amount , and expreess this quotient as a percent 6/30=20%

作者: joywzy 时间: 2003-1-19 21:49 标题: i got it . thank u very much.

then divide this increase by the original amount
so the original amount 是分母

thank u very much . i understank now.

作者: lisaislisa 时间: 2003-1-19 21:58

right
welcome
^^

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