Last visit was: 23 Apr 2026, 12:33 It is currently 23 Apr 2026, 12:33
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
AlexTheTrainer
Joined: 04 Jun 2021
Last visit: 13 Dec 2022
Posts: 73
Own Kudos:
135
 [18]
Given Kudos: 13
Expert
Expert reply
Posts: 73
Kudos: 135
 [18]
1
Kudos
Add Kudos
17
Bookmarks
Bookmark this Post
User avatar
chetan2u
User avatar
GMAT Expert
Joined: 02 Aug 2009
Last visit: 22 Apr 2026
Posts: 11,229
Own Kudos:
45,002
 [1]
Given Kudos: 335
Status:Math and DI Expert
Location: India
Concentration: Human Resources, General Management
GMAT Focus 1: 735 Q90 V89 DI81
Products:
Expert
Expert reply
GMAT Focus 1: 735 Q90 V89 DI81
Posts: 11,229
Kudos: 45,002
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
chetan2u
User avatar
GMAT Expert
Joined: 02 Aug 2009
Last visit: 22 Apr 2026
Posts: 11,229
Own Kudos:
45,002
 [2]
Given Kudos: 335
Status:Math and DI Expert
Location: India
Concentration: Human Resources, General Management
GMAT Focus 1: 735 Q90 V89 DI81
Products:
Expert
Expert reply
GMAT Focus 1: 735 Q90 V89 DI81
Posts: 11,229
Kudos: 45,002
 [2]
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
User avatar
AlexTheTrainer
Joined: 04 Jun 2021
Last visit: 13 Dec 2022
Posts: 73
Own Kudos:
Given Kudos: 13
Expert
Expert reply
Posts: 73
Kudos: 135
Kudos
Add Kudos
Bookmarks
Bookmark this Post
chetan2u
AlexTheTrainer
Yvonne invited x people for dinner and plans to buy a pizza with a diameter of 14 inches. When she discovers that x + z people will be coming to dinner, how much greater in diameter does the pizza need to be, in terms of x and z, so that each person receives the same amount of pizza that Yvonne had originally planned?

(A) \(\frac{49𝜋x}{z}\)
(B) \(\frac{14\sqrt{xz}}{x}\)
(C) \(\frac{49𝜋z}{x}\)
(D) \(\frac{7\sqrt{xz}}{z}\)
(E) \(\frac{z}{7\pi x}\)


The distribution would always be on the area.
So, area =\(\pi r^2=49\pi\), and each of x would get \(\frac{49\pi }{x}\).

If z join in to make the new strength x+z, the requirement of quantity of pizza such that each gets \(\frac{49\pi }{x}\) = \(\frac{49z\pi }{x}\)

Thus the area =\(\pi r^2=\) \(\frac{49z\pi }{x}\)

\(r^2=\frac{49z}{x}......r=7*\frac{\sqrt{z}}{\sqrt{x}}\)= \(\frac{7\sqrt{xz}}{x}\)

The diameter or 2r would be \(\frac{14\sqrt{xz}}{x}\)

B

It would be better to reword the question to ‘what should be the diameter of the pizza now’ from how much greater in diameter does the pizza need to be as the wordings now could suggest we are comparing the two diameters and looking at the increase in diameter.

Writers (like me) need editors because we have blindspots when it comes to our own material. That being said, I am 98% certain that the answer you selected was indeed the additional diameter and not the new diameter. That is, I’m quite certain the question was phrased properly and that you answered it properly.

Would you mind triple checking your work? Very difficult to get rid of a blind spot and you might be right.

Posted from my mobile device
User avatar
chetan2u
User avatar
GMAT Expert
Joined: 02 Aug 2009
Last visit: 22 Apr 2026
Posts: 11,229
Own Kudos:
Given Kudos: 335
Status:Math and DI Expert
Location: India
Concentration: Human Resources, General Management
GMAT Focus 1: 735 Q90 V89 DI81
Products:
Expert
Expert reply
GMAT Focus 1: 735 Q90 V89 DI81
Posts: 11,229
Kudos: 45,002
Kudos
Add Kudos
Bookmarks
Bookmark this Post
AlexTheTrainer
chetan2u
AlexTheTrainer
Yvonne invited x people for dinner and plans to buy a pizza with a diameter of 14 inches. When she discovers that x + z people will be coming to dinner, how much greater in diameter does the pizza need to be, in terms of x and z, so that each person receives the same amount of pizza that Yvonne had originally planned?

(A) \(\frac{49𝜋x}{z}\)
(B) \(\frac{14\sqrt{xz}}{x}\)
(C) \(\frac{49𝜋z}{x}\)
(D) \(\frac{7\sqrt{xz}}{z}\)
(E) \(\frac{z}{7\pi x}\)


The distribution would always be on the area.
So, area =\(\pi r^2=49\pi\), and each of x would get \(\frac{49\pi }{x}\).

If z join in to make the new strength x+z, the requirement of quantity of pizza such that each gets \(\frac{49\pi }{x}\) = \(\frac{49z\pi }{x}\)

Thus the area =\(\pi r^2=\) \(\frac{49z\pi }{x}\)

\(r^2=\frac{49z}{x}......r=7*\frac{\sqrt{z}}{\sqrt{x}}\)= \(\frac{7\sqrt{xz}}{x}\)

The diameter or 2r would be \(\frac{14\sqrt{xz}}{x}\)

B

It would be better to reword the question to ‘what should be the diameter of the pizza now’ from how much greater in diameter does the pizza need to be as the wordings now could suggest we are comparing the two diameters and looking at the increase in diameter.

Writers (like me) need editors because we have blindspots when it comes to our own material. That being said, I am 98% certain that the answer you selected was indeed the additional diameter and not the new diameter. That is, I’m quite certain the question was phrased properly and that you answered it properly.

Would you mind triple checking your work? Very difficult to get rid of a blind spot and you might be right.

Posted from my mobile device


Hi Alex

I have changed my solution to finding the additional diameter. The answer seems to be missing from the options unless I am missing something in the solution.
avatar
Westfolia007
avatar
Current Student
Joined: 02 May 2021
Last visit: 21 Jun 2025
Posts: 22
Own Kudos:
Given Kudos: 11
Location: India
GMAT 1: 690 Q48 V36
GMAT 1: 690 Q48 V36
Posts: 22
Kudos: 11
Kudos
Add Kudos
Bookmarks
Bookmark this Post
chetan2u
Hello sir, I don't think none of the options are matching because I got the answer as 14{ [1-x/z]^1/2 - 1}
User avatar
AlexTheTrainer
Joined: 04 Jun 2021
Last visit: 13 Dec 2022
Posts: 73
Own Kudos:
Given Kudos: 13
Expert
Expert reply
Posts: 73
Kudos: 135
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Sreejit1234
chetan2u
Hello sir, I don't think none of the options are matching because I got the answer as 14{ [1-x/z]^1/2 - 1}

Sreejit1234
chetan2u
Hello sir, I don't think none of the options are matching because I got the answer as 14{ [1-x/z]^1/2 - 1}

Original pizza per person 49pi/x

Additional persons = z

Additional pizza per person = 49pi(z)/x

Calculate additional radius: pi(r^2) = 49pi(z)/x
Additional radius = 7(sqrt z)/(sqrt x) = 7(sqrt xz)/(x)

Additional diameter = 14(sqrt xz)/(x)

Posted from my mobile device
User avatar
chetan2u
User avatar
GMAT Expert
Joined: 02 Aug 2009
Last visit: 22 Apr 2026
Posts: 11,229
Own Kudos:
Given Kudos: 335
Status:Math and DI Expert
Location: India
Concentration: Human Resources, General Management
GMAT Focus 1: 735 Q90 V89 DI81
Products:
Expert
Expert reply
GMAT Focus 1: 735 Q90 V89 DI81
Posts: 11,229
Kudos: 45,002
Kudos
Add Kudos
Bookmarks
Bookmark this Post
AlexTheTrainer
Sreejit1234
chetan2u
Hello sir, I don't think none of the options are matching because I got the answer as 14{ [1-x/z]^1/2 - 1}

Sreejit1234
chetan2u
Hello sir, I don't think none of the options are matching because I got the answer as 14{ [1-x/z]^1/2 - 1}

Original pizza per person 49pi/x

Additional persons = z

Additional pizza per person = 49pi(z)/x

Calculate additional radius: pi(r^2) = 49pi(z)/x
Additional radius = 7(sqrt z)/(sqrt x) = 7(sqrt xz)/(x)

Additional diameter = 14(sqrt xz)/(x)

Posted from my mobile device


Sorry, that is not correct. Calculating additional diameter is not so simple and straightforward.
Additional diameter is not calculated that way. What you have calculated is simply a new pizza for z persons.

If the radius is x and you increase it by y, the new area is \(\pi (r+y)^2\) and not \(\pi y^2\).

The additional diameter is finding the new diameter and subtracting old one from it. That is what additional means.
User avatar
chetan2u
User avatar
GMAT Expert
Joined: 02 Aug 2009
Last visit: 22 Apr 2026
Posts: 11,229
Own Kudos:
45,002
 [1]
Given Kudos: 335
Status:Math and DI Expert
Location: India
Concentration: Human Resources, General Management
GMAT Focus 1: 735 Q90 V89 DI81
Products:
Expert
Expert reply
GMAT Focus 1: 735 Q90 V89 DI81
Posts: 11,229
Kudos: 45,002
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Sreejit1234
chetan2u
Hello sir, I don't think none of the options are matching because I got the answer as 14{ [1-x/z]^1/2 - 1}


Yes, you are correct.
User avatar
AlexTheTrainer
Joined: 04 Jun 2021
Last visit: 13 Dec 2022
Posts: 73
Own Kudos:
Given Kudos: 13
Expert
Expert reply
Posts: 73
Kudos: 135
Kudos
Add Kudos
Bookmarks
Bookmark this Post
chetan2u
Sreejit1234
chetan2u
Hello sir, I don't think none of the options are matching because I got the answer as 14{ [1-x/z]^1/2 - 1}


Yes, you are correct.


YES - you are 100% correct and I’m 100% incorrect! Dangit!

I was soooooo proud of myself for re-writing this question of from memory (originally wrote it in pre-cloud days) but I messed up.

The question should ask: what will the diameter of the additional pizza that Yvonne needs to buy in order to feed the same amount of pizza for each person?

Thanks!

Posted from my mobile device
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
Great job chetan2u !

Saved me lots of frustration

chetan2u
Sreejit1234
chetan2u
Hello sir, I don't think none of the options are matching because I got the answer as 14{ [1-x/z]^1/2 - 1}


Yes, you are correct.

Posted from my mobile device
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,963
Own Kudos:
Posts: 38,963
Kudos: 1,117
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
109785 posts
Tuck School Moderator
853 posts