gwd-24-29滔滔

29 A total of 22 men and 26 women were at a party, and the average (arithmetic mean) age of all of the adults at the party was exactly 35 years. If the average age of the men was exactly 38 years, which of the following was closest to the average age, in years, of the women?

A. 31   B. 31.5   C. 32   D. 32.5   E. 33

Answer 35

答案d,算出来明明是35.1,

suppose the average age of women is x

we have 22*38+26*x=(22+26)*35

then we have x=35-33/13

approximate 32.5

32.5 是近似算出来的

此题让我想起计算GPA

使我脑子糊涂了，22+26算成50了，而且当时算了好几遍就是觉得22+26=50而不是48，不知掉进什么trap里了