Last visit was: 03 May 2026, 02:51 It is currently 03 May 2026, 02:51
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: 03 May 2026
Posts: 110,019
Own Kudos:
Given Kudos: 105,993
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 110,019
Kudos: 812,590
 [14]
Kudos
Add Kudos
14
Bookmarks
Bookmark this Post
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 03 May 2026
Posts: 110,019
Own Kudos:
812,590
 [1]
Given Kudos: 105,993
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 110,019
Kudos: 812,590
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 03 May 2026
Posts: 110,019
Own Kudos:
812,590
 [1]
Given Kudos: 105,993
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 110,019
Kudos: 812,590
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
Matsu12
Joined: 03 Sep 2022
Last visit: 03 Jan 2024
Posts: 6
Own Kudos:
Given Kudos: 2
Location: Mexico
Posts: 6
Kudos: 4
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I have a probably dumb question here... if we take the approach of plugging in numbers x=0 also works, right?
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 03 May 2026
Posts: 110,019
Own Kudos:
812,590
 [1]
Given Kudos: 105,993
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 110,019
Kudos: 812,590
 [1]
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Matsu12
I have a probably dumb question here... if we take the approach of plugging in numbers x=0 also works, right?

Yes, it does, however, x cannot be 0 because we are given that x is a positive number.

If \(x\) is a positive number and \(\frac{1}{2}*\sqrt{x} = 2x\), what is the value of \(x\)?
User avatar
Matsu12
Joined: 03 Sep 2022
Last visit: 03 Jan 2024
Posts: 6
Own Kudos:
Given Kudos: 2
Location: Mexico
Posts: 6
Kudos: 4
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
Matsu12
I have a probably dumb question here... if we take the approach of plugging in numbers x=0 also works, right?

Yes, it does, however, x cannot be 0 because we are given that x is a positive number.


If \(x\) is a positive number and \(\frac{1}{2}*\sqrt{x} = 2x\), what is the value of \(x\)?

Posted from my mobile device

You smart cookie! Thanks
User avatar
Student102
Joined: 23 May 2025
Last visit: 26 May 2025
Posts: 1
Posts: 1
Kudos: 0
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I did not quite understand the solution. HOw did you get X=4x by cross multiplying?
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 03 May 2026
Posts: 110,019
Own Kudos:
Given Kudos: 105,993
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 110,019
Kudos: 812,590
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Student102

Bunuel
Official Solution:

If \(x\) is a positive number and \(\frac{1}{2}*\sqrt{x} = 2x\), what is the value of \(x\)?

A. \(0\)
B. \(\frac{1}{16}\)
C. \(\frac{1}{4}\)
D. \(\frac{1}{2}\)
E. \(1\)


Cross-multiply: \(\sqrt{x} = 4x\)

Square both sides of the equation to eliminate the square root: \(x = 16x^2\)

Given that \(x\) is a positive number, we can safely divide both sides by \(x\): \(1 = 16x\). This gives us \(x = \frac{1}{16}\).


Answer: B
I did not quite understand the solution. HOw did you get X=4x by cross multiplying?

\(\frac{1}{2}*\sqrt{x} = 2x\)

Multiply by 2:

\(\sqrt{x} = 4x\)
User avatar
Amarinelo
Joined: 02 Apr 2025
Last visit: 21 Oct 2025
Posts: 2
Own Kudos:
Given Kudos: 12
Posts: 2
Kudos: 1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Could we approach this any different?
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 03 May 2026
Posts: 110,019
Own Kudos:
Given Kudos: 105,993
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 110,019
Kudos: 812,590
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Amarinelo
Could we approach this any different?

Alternatively, you could simply plug in the options. Another discussion of this question can be found here:

https://gmatclub.com/forum/if-x-is-a-po ... 49288.html

Hope it helps.
User avatar
kouassidrissa047
Joined: 11 May 2025
Last visit: 27 Oct 2025
Posts: 46
Given Kudos: 1
Posts: 46
Kudos: 0
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I like the solution - it’s helpful.
User avatar
martina3750
Joined: 24 Apr 2025
Last visit: 05 Jan 2026
Posts: 6
Own Kudos:
Given Kudos: 212
Posts: 6
Kudos: 3
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I like the solution - it’s helpful.
User avatar
Nicopaz
Joined: 25 Nov 2025
Last visit: 21 Apr 2026
Posts: 2
Posts: 2
Kudos: 0
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I like the solution - it’s helpful.
User avatar
Nicopaz
Joined: 25 Nov 2025
Last visit: 21 Apr 2026
Posts: 2
Posts: 2
Kudos: 0
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I like the solution - it’s helpful.
User avatar
Condemned13
Joined: 29 Nov 2015
Last visit: 25 Dec 2025
Posts: 6
Posts: 6
Kudos: 0
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I like the solution - it’s helpful. Heuristic is x < 1, and it has to be power of 4 of something.
Moderators:
Math Expert
110019 posts
Founder
43197 posts