想请教一道数学题目

草木染湘

124.If n is an integer, is
an integer?(B)
(1)
is an integer×(2)
is an integer√
谢谢啦

草木染湘

还想请问一道，为什么我做出来是(E)   谢谢啦
134. 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?  (C)
(1)  
(2) W=w+5

草木染湘

134. 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?  (C)
(1) 1/10<W/774<1/9
(2) W=w+5
不好意思啦

cola5117

抛砖引玉一下
很简单可以看出只有A或者B是推不出什么东西的..
我们需要验证 W/774 - w/362 < 10% 这个结论
同时有A和B我们可以得出
W/774 - （W-5）/362 = W/774 - W/774 × 774/362 + 5/362
< 1/9 - 1/10 × 774/362 + 5/362 < 1/9 - 2× 1/10 + 5/362 < 10% 显然成立
所以选C吧

草木染湘

thanks...