GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 26 Aug 2019, 02:54

### 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

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

Track

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

# M05-01

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 57298

### Show Tags

16 Sep 2014, 00:24
1
00:00

Difficulty:

5% (low)

Question Stats:

94% (00:35) correct 6% (00:43) wrong based on 225 sessions

### HideShow timer Statistics

If $$a$$, $$b$$, and $$c$$ are 3 different integers and $$a * b * c = 55$$, what is the value of c?

(1) a = 5

(2) b = 11

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 57298

### Show Tags

16 Sep 2014, 00:24
1
Official Solution:

Statement (1) by itself is insufficient. We don't know the value of $$b$$.

Statement (2) by itself is insufficient. We don't know the value of $$a$$.

Statements (1) and (2) combined are sufficient. Taking both statements together, $$a = 5$$ and $$b = 11$$, therefore $$c = 1$$.

_________________
Intern
Joined: 23 Dec 2015
Posts: 3

### Show Tags

31 Jul 2019, 19:52
Hi Bunuel,

shoudnt the answer be E? since in either case, C can take up a value of 1, -1. Am i missing anything? A,b,c are distinct integers not that they are positive only.
Math Expert
Joined: 02 Sep 2009
Posts: 57298

### Show Tags

31 Jul 2019, 23:11
san01sin wrote:
Hi Bunuel,

shoudnt the answer be E? since in either case, C can take up a value of 1, -1. Am i missing anything? A,b,c are distinct integers not that they are positive only.

If a = 5 and b = 11, then c can only be 1 for abc to be equal to 55. If c = -1, then abc = -55.
_________________
Intern
Joined: 16 May 2019
Posts: 42

### Show Tags

06 Aug 2019, 08:37
Bunuel wrote:
If $$a$$, $$b$$, and $$c$$ are 3 different integers and $$a * b * c = 55$$, what is the value of c?

(1) a = 5

(2) b = 11

For this problem, I found it useful to start by creating a factor tree. 55 breaks down into 5 x 11, both prime numbers, so the only integer left has to be 1. The rest of the question deals with how negatives and positives interact, since it would not be safe to assume that integers means only positive ones.

Statement (1), as the official solution points out, tells us nothing about "b," so we cannot speculate on which of the other integers "c" may be. Out go (A) and (D).

Statement (2) also reveals nothing about one of the other two unknowns, this time "a," so we are in the same boat as before. (B) is out.

Taken together, we know a * b * c = 55 and, by substitution, that (5) * (11) * c = 55. We could solve this one algebraically, but there is no need, once we understand that a positive times a positive times some unknown to yield a positive product must mean that the unknown is positive itself. Thus, "c" can only be 1, and (C) is the answer.
Re: M05-01   [#permalink] 06 Aug 2019, 08:37
Display posts from previous: Sort by

# M05-01

Moderators: chetan2u, Bunuel