Last visit was: 23 Jan 2025, 13:41 It is currently 23 Jan 2025, 13:41
Close
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
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.
Close
Request Expert Reply
Confirm Cancel
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 23 Jan 2025
Posts: 98,904
Own Kudos:
Given Kudos: 91,889
Products:
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 98,904
Kudos: 696,116
 [23]
2
Kudos
Add Kudos
20
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 23 Jan 2025
Posts: 98,904
Own Kudos:
696,116
 [8]
Given Kudos: 91,889
Products:
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 98,904
Kudos: 696,116
 [8]
4
Kudos
Add Kudos
4
Bookmarks
Bookmark this Post
General Discussion
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 23 Jan 2025
Posts: 98,904
Own Kudos:
Given Kudos: 91,889
Products:
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 98,904
Kudos: 696,116
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
fdfd97
Joined: 14 Mar 2023
Last visit: 27 May 2024
Posts: 40
Own Kudos:
Given Kudos: 14
Posts: 40
Kudos: 31
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I have a doubt regarding the 2nd statement. If you divide both sides by x^2, won't we get 1= x from x^2 = X^3.

Please help clarify my doubt. I chose Option D, since I thought that we can get the value for x from each statement.


Bunuel
Official Solution:


What is the value of \(x^2\)?


(2) \(x^2 = x^3\):

\(x^2 - x^3 = 0\)

\(x^2 (1 - x) = 0\)

\(x = 0\) or \(x =1\).

Therefore, \(x^2 = 0\) or \(x^2 = 1\). Not sufficient.


Answer: A
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 23 Jan 2025
Posts: 98,904
Own Kudos:
Given Kudos: 91,889
Products:
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 98,904
Kudos: 696,116
Kudos
Add Kudos
Bookmarks
Bookmark this Post
fdfd97
I have a doubt regarding the 2nd statement. If you divide both sides by x^2, won't we get 1= x from x^2 = X^3.

Please help clarify my doubt. I chose Option D, since I thought that we can get the value for x from each statement.


Bunuel
Official Solution:


What is the value of \(x^2\)?


(2) \(x^2 = x^3\):

\(x^2 - x^3 = 0\)

\(x^2 (1 - x) = 0\)

\(x = 0\) or \(x =1\).

Therefore, \(x^2 = 0\) or \(x^2 = 1\). Not sufficient.


Answer: A

Note that we cannot divide x^2 = x^3 by x^2 because x^2 (x) can be 0 and division by zero is not allowed. By dividing by x^2, you would be incorrectly assuming that x^2 does not equal zero, potentially excluding a valid solution (observe that x = 0 satisfies the equation). As a rule, never reduce an equation by a variable (or by an expression containing a variable) if you are not certain that the variable (or expression with the variable) does not equal zero. Remember, we cannot divide by zero.
User avatar
fdfd97
Joined: 14 Mar 2023
Last visit: 27 May 2024
Posts: 40
Own Kudos:
Given Kudos: 14
Posts: 40
Kudos: 31
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Oh right, that totally slipped out of my mind while solving the question, that's why I got it's value as 1. Thanks.
User avatar
BottomJee
User avatar
Retired Moderator
Joined: 05 May 2019
Last visit: 10 Oct 2024
Posts: 996
Own Kudos:
Given Kudos: 1,005
Affiliations: GMAT Club
Location: India
GMAT Focus 1: 645 Q82 V81 DI82
GMAT 1: 430 Q31 V19
GMAT 2: 570 Q44 V25
GMAT 3: 660 Q48 V33
GPA: 3.26
WE:Engineering (Manufacturing)
Products:
GMAT Focus 1: 645 Q82 V81 DI82
GMAT 3: 660 Q48 V33
Posts: 996
Kudos: 1,029
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I think this is a high-quality question and I agree with explanation.
avatar
ritwick2
Joined: 28 Sep 2023
Last visit: 10 Apr 2024
Posts: 3
Given Kudos: 2
GMAT 1: 580 Q38 V30
GMAT 1: 580 Q38 V30
Posts: 3
Kudos: 0
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
Official Solution:


What is the value of \(x^2\)?

(1) \(x = \sqrt{2x - 1}\)

Square:

\(x^2 = 2x - 1\)

\(x^2 - 2x + 1 = 0\)

\((x-1)^2 = 0\)

\(x -1 = 0\)

\(x = 1\)

Thus, \(x^2 = 1\). Sufficient/

(2) \(x^2 = x^3\):

\(x^2 - x^3 = 0\)

\(x^2 (1 - x) = 0\)

\(x = 0\) or \(x =1\).

Therefore, \(x^2 = 0\) or \(x^2 = 1\). Not sufficient.


Answer: A
Hi Bunuel, I used this method in the first statement after squaring both sides: x^2=2x-1 -> X^2-2x=-1 -> x(x-2)=-1 -> x=(-1) or (1). Why is this incorrect since we've used the same method in statement 2.
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 23 Jan 2025
Posts: 98,904
Own Kudos:
Given Kudos: 91,889
Products:
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 98,904
Kudos: 696,116
Kudos
Add Kudos
Bookmarks
Bookmark this Post
ritwick2
Bunuel
Official Solution:


What is the value of \(x^2\)?

(1) \(x = \sqrt{2x - 1}\)

Square:

\(x^2 = 2x - 1\)

\(x^2 - 2x + 1 = 0\)

\((x-1)^2 = 0\)

\(x -1 = 0\)

\(x = 1\)

Thus, \(x^2 = 1\). Sufficient/

(2) \(x^2 = x^3\):

\(x^2 - x^3 = 0\)

\(x^2 (1 - x) = 0\)

\(x = 0\) or \(x =1\).

Therefore, \(x^2 = 0\) or \(x^2 = 1\). Not sufficient.


Answer: A
Hi Bunuel, I used this method in the first statement after squaring both sides: x^2=2x-1 -> X^2-2x=-1 -> x(x-2)=-1 -> x=(-1) or (1). Why is this incorrect since we've used the same method in statement 2.

In the second statement, x^2(1 - x) equals 0, so either x^2 or (1 - x) must be 0 due to the zero product property. However, in the first statement, x(x - 2) equals -1, which is different. Here, you cannot conclude that x equals -1 or 1. The rules for solving equations are different when the product is zero compared to when it's a non-zero value.
Moderators:
Math Expert
98904 posts
Founder
39653 posts