A total of \(30\) percent of the geese included in a certain migration study were male. If some of the geese migrated

[M7MBA]

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

Answer: B

Source: GMAT Prep

[Scott@TargetTestPrep]

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

Answer: B

Solution:

We can let t = the total number of geese before migration; thus, the number of male geese = 0.3t, and the number of female geese = 0.7t. If we let the number of migrating geese = m, then the number of male migrating geese = 0.2m and the number of female migrating geese = 0.8m.

Thus, the migration rate for the male geese is 0.2m/0.3t = 2m/3t and the migration rate for the female geese is 0.8m/0.7t = 8m/7t.

Thus, the ratio of male migration rate to female migration rate is:

(2m/3t)/(8m/7t) = (7t x 2m)/(3t x 8m) = (14mt)/(24mt) = 14/24 = 7/12.

Answer: B

[Brent@GMATPrepNow]

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

Answer: B

We can skip algebra and just find some values that satisfy the given information.

A total of 30 percent of the geese included in a certain migration study were male.
So, it could be the case that there where 100 geese in the STUDY, which means 30 were male and 70 were female.

Some of the geese migrated during the study and 20 percent of the migrating geese were male
So it could be the case 10 geese from the study migrated, which means 2 were male and 8 were female.

What was the ratio of the migration rate for the male geese to the migration rate for the female geese?
The migration rate for the males = 2/30 = 1/15
The migration rate for the females = 8/70 = 4/35

So, the ratio of the migration rate for the male geese to the migration rate for the female geese = (1/15)/(4/35)
= (1/15)(35/4)
= 35/60
= 7/12

Answer: B

Source: GMAT Prep