Last visit was: 25 Apr 2026, 13:16 It is currently 25 Apr 2026, 13:16
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: 25 Apr 2026
Posts: 109,831
Own Kudos:
Given Kudos: 105,886
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,831
Kudos: 811,259
 [12]
Kudos
Add Kudos
11
Bookmarks
Bookmark this Post
User avatar
sumitkrocks
Joined: 02 Jul 2017
Last visit: 22 Aug 2023
Posts: 637
Own Kudos:
Given Kudos: 333
Location: India
Concentration: Strategy, Technology
GMAT 1: 730 Q50 V39
GMAT 2: 710 Q50 V36
Products:
GMAT 2: 710 Q50 V36
Posts: 637
Kudos: 879
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
TestPrepUnlimited
Joined: 17 Sep 2014
Last visit: 30 Jun 2022
Posts: 1,223
Own Kudos:
1,138
 [1]
Given Kudos: 6
Location: United States
GMAT 1: 780 Q51 V45
GRE 1: Q170 V167
Expert
Expert reply
GMAT 1: 780 Q51 V45
GRE 1: Q170 V167
Posts: 1,223
Kudos: 1,138
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
ThatDudeKnows
Joined: 11 May 2022
Last visit: 27 Jun 2024
Posts: 1,070
Own Kudos:
Given Kudos: 79
Expert
Expert reply
Posts: 1,070
Kudos: 1,030
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel

A quarter circle with radius 4 cm has a circle inscribed in it as shown above. What is the diameter of the inscribed circle ?


A. \(\frac{3}{1+\sqrt{2}}\)

B. \(\frac{4}{1+\sqrt{2}}\)

C. \(\frac{5}{1+\sqrt{2}}\)

D. \(\frac{6}{1+\sqrt{2}}\)

E. \(\frac{8}{1+\sqrt{2}}\)


Attachment:
1045966_f946153db51a405bb0a4234ae0109dc2.png


Ballpark, please!

The radius of the quarter circle is 4. Is the diameter of the inscribed circle larger than that or smaller? Smaller. How much smaller? Is it 10%? 50%? 90% I don't know, let's say it's 3.5, maybe a touch less.
Awesome, that's the diameter of the inscribed circle, which is what we are asked to find.
Let's look at the answer choices. All of the denominators are the same and are roughly 1+1.4, so denominator is 2.4. We need a numerator that's 2.4 * 3.5 = 8.4. Only one answer choice is close.

Answer choice E.


ThatDudeKnowsBallparking
User avatar
VIGHNESHKAMATH
Joined: 28 Sep 2021
Last visit: 21 Nov 2022
Posts: 145
Own Kudos:
Given Kudos: 259
Posts: 145
Kudos: 54
Kudos
Add Kudos
Bookmarks
Bookmark this Post
TestPrepUnlimited
Bunuel

A quarter circle with radius 4 cm has a circle inscribed in it as shown above. What is the diameter of the inscribed circle ?


A. \(\frac{3}{1+\sqrt{2}}\)

B. \(\frac{4}{1+\sqrt{2}}\)

C. \(\frac{5}{1+\sqrt{2}}\)

D. \(\frac{6}{1+\sqrt{2}}\)

E. \(\frac{8}{1+\sqrt{2}}\)


The radius of the big circle is consisted of two segments OA and AB. Let AB = x, then \(OA = \sqrt{2}*x\) and \(AB = x\).

Then OB = \(\sqrt{2}x + x = 4\)

\(x = \frac{4}{\sqrt{2} + 1}\) however the question is asking for diameter which is 2x.

Ans: E

How did you get OA?

Thank You
Vighnesh
User avatar
Fdambro294
Joined: 10 Jul 2019
Last visit: 20 Aug 2025
Posts: 1,331
Own Kudos:
Given Kudos: 1,656
Posts: 1,331
Kudos: 772
Kudos
Add Kudos
Bookmarks
Bookmark this Post
VIGHNESHKAMATH
TestPrepUnlimited
Bunuel

A quarter circle with radius 4 cm has a circle inscribed in it as shown above. What is the diameter of the inscribed circle ?


A. \(\frac{3}{1+\sqrt{2}}\)

B. \(\frac{4}{1+\sqrt{2}}\)

C. \(\frac{5}{1+\sqrt{2}}\)

D. \(\frac{6}{1+\sqrt{2}}\)

E. \(\frac{8}{1+\sqrt{2}}\)


The radius of the big circle is consisted of two segments OA and AB. Let AB = x, then \(OA = \sqrt{2}*x\) and \(AB = x\).

Then OB = \(\sqrt{2}x + x = 4\)

\(x = \frac{4}{\sqrt{2} + 1}\) however the question is asking for diameter which is 2x.

Ans: E

How did you get OA?

Thank You
Vighnesh

(1st)
The center of the inscribed circle (call it point O) is also the geometric center of the quarter circle

Draw a line segment from vertex B to the point of Tangency on the circumference (call it point D)

BD passes through center O of the inscribed circle

OD = r = radius of inscribed circle

(2nd)

Concept: a radius drawn to a tangent line at the point of Tangency creates a 90 degree angle with the tangent line

Draw 2 line segments from center O to sides BA and BC

This quadrilateral is a square with side = r

And diagonal of this square = BO = r * sqrt(2)

(3rd)

BO + OD = radius of the quarter circle = 4

r * sqrt(2) + r = 4

r * [(sqrt(2) + 1)] = 4

r = 4 / (sqrt(2) + 1)

Double it to get the diameter

8 / (sqrt(2) + 1)

*E*

Posted from my mobile device
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,985
Own Kudos:
Posts: 38,985
Kudos: 1,118
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Automated notice from GMAT Club BumpBot:

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

This post was generated automatically.
Moderators:
Math Expert
109831 posts
Tuck School Moderator
852 posts