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 fo such doctorates in mathematics 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 form the 1972-1972 school year to 1986-1987 school year, was the decrease less than 10 percent?

1) 1/10<W/774<1/9

2) W = w+5

答案选C， 题目很长，麻烦大家耐心看看。这是我目前做到比较challenging 的题目了。。

题目其实就是问：is (W-w)/W<10%?

1)可得：77.4<W<86, 2)可得：(W-w)/W=5/W

很明显，1)、2)都无法单独回答；1)+2)则可得“Yes”——随便取个最小的W＝78，5/W也小于10％。