跪求GWD MATH6-14的解法

zoe305 · 发表于 2010-4-3 22:57:51

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

这条题目读了半天也不是很理解它的意思，这里的migration就是迁移的意思吗？只说了雄性迁移也没将雌性迁不迁啊？怎么算比例啊？
希望牛人帮我解答一下，谢谢~~~

felifeli · 发表于 2010-4-3 23:18:21

migrate male 30%, so, migrate female 70% (1-30%).
假设migrate 了 X 只geese
那么其中male 为 20%X, female 为 80%X

migrate rate for male: 20%X/30%
migrate rate for female: 80%X/70%

So ratio:
20%X/30%:80%X/70%=7/12

zoe305 · 发表于 2010-4-3 23:21:48

恩，结合你的解答把题目又仔细看了一遍终于理顺了，万分感谢~~~

跪求GWD MATH6-14的解法

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