BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

probability D.S

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 62
Joined: Tue Mar 16, 2010 8:27 am
Thanked: 1 times

probability D.S

by raunakrajan » Wed Jun 30, 2010 3:44 am
If a number n is pulled out of a hat at random, what is the probability that( 1/2)n - 2 ≥ 0?

(1) There are 6 numbers in the hat and each number is an integer.

(2) For every value of n in the hat, 1 ≤ n ≤ 30.

ANSWER IS E
but how to go about this?
Top
Source: — Data Sufficiency |
User avatar
GMAT Instructor
Posts: 147
Joined: Tue Aug 25, 2009 7:57 pm
Location: New York City
Thanked: 76 times
Followed by:17 members
GMAT Score:770

by Rich@VeritasPrep » Wed Jun 30, 2010 4:02 am
First, you can rewrite the inequality in the prompt:

(1/2)n - 2 >= 0

(1/2) n >= 2

n >= 4

So the question really asks for the probability that n >= 4.

(1) doesn't tell you anything, because we don't know what integers are in the hat.

(2) also doesn't tell you anything, because although we know every number in the hat is between 1 and 30 inclusive, we don't know how many are equal to 4 or greater.

(1) and (2) together still don't tell you anything. We know there are 6 integers in the hat, and we know that all of the integers are between 1 and 30 inclusive, but there's no way of telling how many of the integers are greater than or equal to 4.
Rich Zwelling
GMAT Instructor, Veritas Prep
Top
Post new topic Post Reply
• Page 1 of 1