geese rates!

[mariah]

Of a group of geese in a certain research, 30% is male, and 20% of the migrating gooses are male. What is the ratio of the male goose migrating rate to the female goose migrating rate?

[Stuart@KaplanGMAT]

Of a group of geese in a certain research, 30% is male, and 20% of the migrating gooses are male. What is the ratio of the male goose migrating rate to the female goose migrating rate?

Picking Numbers:

Let's say we have 100 geese.

So, 30 are male, 70 are female.

Let's say that 50 of the geese migrate.

Of these 50, 20% = 10 are male, 40 are female.

So, the male rate of migration is 10/30 = 1/3
The female rate of migration is 40/70 = 4/7

The ratio of male to female migration rate is:

(1/3)/(4/7) = (1/3)*(7/4) = 7/12

However, let's say 40 of the geese migrate.

Of these 40, 20% = 8 are male, 32 are female.

So, the male rate of migration is 8/30 = 4/15
The female rate of migration is 32/70 = 16/35

The ratio of male to female migration rate is:

(4/15)/(16/35) = (4/15)*(35/16) = 140/240 = 14/24 = 7/12

So, it doen't matter what numbers we pick, we'll get the same answer.

Of course, if you had provided answer choices (and if none of those choices were "it cannot be determined from the information given"), we wouldn't have needed to double check. Please always provide answer choices (and cite your source) so we can treat your query like a real GMAT question on test day!

Algebraically:

((20%)/(30%))/((80%)/(70%)) = (2/3)/(8/7) = (2/3)*(7/8) = 14/24 = 7/12

[mariah]

oa 7/12