Q14:
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)]
A. 1/4
B. 7/12
C. 2/3
D. 7/8
E. 8/7

MINE E

ANS:B

不明白

题目说公鹅30%，母鹅70%；迁移的鹅中20%为公，80%为母。

则可以设一共有A只鹅~迁移了B只

所以公鹅的迁移率为20%B/30%A

母鹅的迁移率为80%B/70%A...

两者之比，B、A可以消去

就是2楼给的那个答案，选B...