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

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

GMAT Diagnostic Test Question 20 [#permalink]
06 Jun 2009, 21:58

Expert's post

6

This post was BOOKMARKED

GMAT Diagnostic Test Question 20 Field: Statistics Difficulty: 700

If a, b & c are integers and a < b < c. Are a, b, c consecutive integers?

(1) The median of {a!, b!, c!} is an odd number. (2) c! is a prime number.

A. Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient B. Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient D. EACH statement ALONE is sufficient E. Statements (1) and (2) TOGETHER are NOT sufficient _________________

A. The factorial of a negative number is undefined.

B. 0!=1.

C. Only two factorials are odd: 0!=1 and 1!=1.

D. Factorial of a number which is prime is 2!=2.

(1) The median of {a!, b!, c!} is an odd number. This implies that b!=odd. Thus b is 0 or 1. But if b=0, then a is a negative number, so in this case a! is not defined. Therefore a=0 and b=1, so the set is {0!, 1!, c!}={1, 1, c!}. Now, if c=2, then the answer is YES but if c is any other number then the answer is NO. Not sufficient.

(2) c! is a prime number. This implies that c=2. Not sufficient.

(1)+(2) From above we have that a=0, b=1 and c=2, thus the answer to the question is YES. Sufficient.

Re: GMAT Diagnostic Test Question 20 [#permalink]
18 Feb 2014, 07:12

Why is "a" assumed to be 0? "a" can take any value right? only b! is odd and nowhere it is given that "a" is lesser than b? Am I missing something here?

Re: GMAT Diagnostic Test Question 20 [#permalink]
18 Feb 2014, 07:53

Expert's post

stuffs88 wrote:

Why is "a" assumed to be 0? "a" can take any value right? only b! is odd and nowhere it is given that "a" is lesser than b? Am I missing something here?

Actually it is given: "If a, b & c are integers and a < b < c. Are a, b, c consecutive integers?" _________________

Re: GMAT Diagnostic Test Question 19 [#permalink]
13 Mar 2014, 17:54

dzyubam wrote:

Explanation: Official Answer: C

Note that:

A. The factorial of a negative number is undefined.

B. 0!=1.

C. Only two factorials are odd: 0!=1 and 1!=1.

D. Factorial of a number which is prime is 2!=2.

(1) The median of {a!, b!, c!} is an odd number. This implies that b!=odd. Thus b is 0 or 1. But if b=0, then a is a negative number, so in this case a! is not defined. Therefore a=0 and b=1, so the set is {0!, 1!, c!}={1, 1, c!}. Now, if c=2, then the answer is YES but if c is any other number then the answer is NO. Not sufficient.

(2) c! is a prime number. This implies that c=2. Not sufficient.

(1)+(2) From above we have that a=0, b=1 and c=2, thus the answer to the question is YES. Sufficient.

The correct answer is C

I think only B is ok because - c! is prime number -> c = 2 - a < b < c and a, b, c is integers -> a = 0, b= 1

Re: GMAT Diagnostic Test Question 19 [#permalink]
13 Mar 2014, 19:59

Expert's post

tiendungdo wrote:

dzyubam wrote:

Explanation: Official Answer: C

Note that:

A. The factorial of a negative number is undefined.

B. 0!=1.

C. Only two factorials are odd: 0!=1 and 1!=1.

D. Factorial of a number which is prime is 2!=2.

(1) The median of {a!, b!, c!} is an odd number. This implies that b!=odd. Thus b is 0 or 1. But if b=0, then a is a negative number, so in this case a! is not defined. Therefore a=0 and b=1, so the set is {0!, 1!, c!}={1, 1, c!}. Now, if c=2, then the answer is YES but if c is any other number then the answer is NO. Not sufficient.

(2) c! is a prime number. This implies that c=2. Not sufficient.

(1)+(2) From above we have that a=0, b=1 and c=2, thus the answer to the question is YES. Sufficient.

The correct answer is C

I think only B is ok because - c! is prime number -> c = 2 - a < b < c and a, b, c is integers -> a = 0, b= 1

Can you give me explanation? tks alot.

The problem with statement 2 alone is that a and b can be negative too. c we know is 2 but a can be -2 and b can be 1 or many other cases. Only statement 1 uses a! and b! which implies that a and b cannot be negative and hence should be 0 and 1. Therefore, we need both statements to get the answer.