GWD一题求助

legendends

A total of 30 percent of the geese included in a certain migration study were male.  If some of the geese migrated during the study and 20 percent of the migrating geese were male, what was the ratio of the migration rate for the male geese to the migration rate for the female geese?

[Migration rate for geese of a certain sex = (number of geese of that sex migrating) / (total number of geese of that sex)]  B

 

 

A.      1/4

B.      7/12

C.      2/3

D.     7/8

E.      8/7

missdandan

设 the number of the migrating geeses 为n，则：

the ratio＝(0.2n/0.3)/(0.8n/0.7)=7/12

请指正

legendends

谢谢！ 我原以为是30%G=Male， 20%M=Male， 然后一个式子要代进去算得。 忽忽~~