Hi Palak-gmat,
Ratio questions can be handled in a number of different ways, depending on how you choose to organize the given information.
We're told that there are 3 types of rodents: Rats, Mice and Squirrels. We're asked if there are MORE than 3 times as many Rats as Squirrels. This is a YES/NO question.
1) The ratio of Squirrels to the TOTAL rodent population is 1 to 5.
This Fact tells us that 20% of the rodents are Squirrels, so the remaining 80% are Rats and Mice. Unfortunately, we don't know the exact percents, so there's no way to know whether there are 3 times as many Rats as Squirrels.
IF it's....
10% Rats and 70% Mice, then the answer to the question is NO.
70% Rats and 10% Mice, then the answer to the question is YES.
Fact 1 is INSUFFICIENT.
2) The ratio of Squirrels to Mice is 2 to 1.
This Fact tells us that there are twice as many Squirrels as Mice. While it does limit the fraction that could be Squirrels and Mice (at the highest, it would be about 2/3 Squirrels, 1/3 Mice and almost 0 Rats; at the lowest it could be almost 0 Squirrels, almost 0 Mice and almost all Rats), it does not define the relationship between the number of Rats and the number of Squirrels.
Fact 2 is INSUFFICIENT.
Combined, we know...
20% of the total are Squirrels
10% of the total are Mice (since the ratio of Squirrels to Mice is 2:1)
By extension, 70% of the rodents must be Rats and the answer to the question is YES.
Combined, SUFFICIENT.
Final Answer: C
GMAT assassins aren't born, they're made,
Rich
