75: 做一个实验，male birds有多少比重，迁徙的male birds有多少比重，问一个ratio=(迁徙的male birds/总male birds)/（迁徙的female birds/总female birds） 按照公式算就好了 Q14: B 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)]
Suppose that total number of geese=x and that the number of migrating geese=y, then according to the conditions given, migration rate for male geese=0.2y/0.3x migration rate for female geese=0.8y/0.7x Therefore, the ratio of the migration rate for the male geese to the migration rate for the female geese=0.2y/0.3x(除以）0.8y/0.7x=7/12 是要的这个式子么？
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发表于 2010-10-25 02:46:39
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