|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
02 Jun 2018, 13:36
Kudos
Bookmarks
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
63% (01:28) correct
37%
(01:29)
wrong
based on 492
sessions
History
Date
Time
Result
Not Attempted Yet
There are 20 books in a bookcase. If one book is selected at random, what is the probability that the book is either a hardback or a novel?
(1) 8 books in the bookcase are novel books and 10 books are hardbacks.
(2) 3 books in the bookcase are hardback novels
(1) 8 books in the bookcase are novel books and 10 books are hardbacks.
(2) 3 books in the bookcase are hardback novels
02 Jun 2018, 13:45
Kudos
Bookmarks
Bunuel
We'll use numbers to help us understand the logic behind the question.
This is an Alternative approach.
(1) Say all 8 of the novels are hardbacks. Then 10 of the books are hardbacks or novels and the probability is 10/20. Say none of the novels are hardbacks. Then 18 books are novels or hardbacks and the answer is 18/20.
Insufficient.
(2) We have no information on the number of non-hardback novels and can pick easy numbers such as 0 or to 1. In the first case the probability is 3/20 and in the second 4/20.
Insufficient.
Combined:
So 3 books are hardback novels meaning that 10 - 3 = 7 are hardbacks that aren't novels and 8 - 3 = 5 are novels that aren't hardbacks.
So there are 3 + 7 + 5 = 15 books that are novels or hardbacks and the probability must be 15/20.
Sufficient.
(C) is our answer.
02 Jun 2018, 13:59
Kudos
Bookmarks
Solution
Given:
• Number of books in the bookcase = 20
To find:
• If one book is selected at random, the probability of it being either hardback or novel
Analysing Statement 1
• As per the information provided in Statement 1, 8 books are novel books and 10 books are hardbacks
- o But from this statement, we cannot find out whether there are any books which are novel and have hardcover or vice versa.
Hence, statement 1 is not sufficient to answer
Analysing Statement 2
• As per the information provided in Statement 2, 3 novels are hardback
- o But we don’t know whether there are books which are only novel without hardcover or books with hardcover which are not novel.
Hence, statement 2 is not sufficient to answer
Combining Both Statements
We already know 8 novel books and 10 hardbacks books are there, out of which 3 novels are hardbacks.
- • Therefore the probability = \(\frac{(8 + 10 – 3)}{20} = \frac{3}{4}\)
Hence, the correct answer is option C.
Answer: C
