问到数学题

miguel29

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
Answer: B

谁会做，教我一下，马上步骤详细点，我数学很差的。。谢谢了

tangbin1985

原来男女比例3：7
迁徙的里面男女比例2：8
这样，迁徙的男的数量占男总量的比例是2/3，迁徙的女数量占女总数的比例是8/7，
最后得出答案2/3 :8/7=7：12

wanderingtim

晕，这道题看了半天才看懂。
之前的3：7是样本男女比例
2：8是迁徙男女比例，
求男女迁徙“率”比例，
即2/3:8/7=7:12
我这么理解应该没错吧~~

miguel29

强。。。明白了，谢谢啦