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 GMAT = (number of geese of that GMAT migrating) / (total number of geese of that GMAT)
A. 1/4
B. 7/12
C. 2/3
D. 7/8
E. 8/7
Let the total number of geese = 100.
Since 30% of the geese are male, male geese = 30 and female geese = 70.
Let the total number of migrating geese = 10.
Since 20% of the migrating geese are male, there are 2 male migrating geese and 8 female migrating geese.
male migration rate = (migrating males)/(all males) = 2/30 = 1/15.
female migration rate = (migrating females)/(all females) = 8/70 = 4/35.
Resulting ratio:
(male migration rate)/(female migration rate) = (1/15) / (4/35) = (1/15) * (35/4) = 7/12.
The correct answer is
B.
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