theCodeToGMAT wrote:If a number is drawn at random from the first 1000 positive integers, what is the probability of selecting a refined number?
(1) Any refined number must be divisible by 22.
(2) A refined number is any even multiple of 11.
OA B
Target question: What is the probability of selecting a refined number?
Statement 1: Any refined number must be divisible by 22.
This just provides a necessary condition of being a refined number. It does not mean that
ANY number divisible by 22 is a refined number.
There might be other features of refined numbers that would further restrict the number of refined numbers from 1 to 1000.
Example: Any prime number must be a integer. However, although 6 is an integer does not mean that it must be a prime number.
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: A refined number is any even multiple of 11.
Hmmmmm, not sure about this one. The term "even multiple" MAY BE intuitively apparent, but I believe the GMAT test-makers would provide additional text to avoid any ambiguity.
Presumably even multiples of 11 are 22, 44, 66, 88, etc.
Now that we can identify ALL of the refined numbers from 1 to 1000, we can definitely answer the
target question with certainty.
So, statement 2 is SUFFICIENT
Answer =
B
Cheers,
Brent
