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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at the speed of 60 rpm and the mixer is mixing at the rate of 8 rpm. What is the diameter of the mixing wheel if the radius of the smaller (drive) wheel is 2 inches?

12 15 25 30 32 _________________

Your attitude determines your altitude Smiling wins more friends than frowning

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at the speed of 60 rpm and the mixer is mixing at the rate of 8 rpm. What is the diameter of the mixing wheel if the radius of the smaller (drive) wheel is 2 inches?

12 15 25 30 32

I can't image this machine. Could someone explain this or upload the image for me?

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at the speed of 60 rpm and the mixer is mixing at the rate of 8 rpm. What is the diameter of the mixing wheel if the radius of the smaller (drive) wheel is 2 inches?

12 15 25 30 32

I am assuming that smaller wheel is driven directly by the engine at 60 rpm.. i.e speed of smaller wheel is 60 too. in that case using nr=NR i get R=15.

But 3 connected wheel is misleading. It seems to indicate a gear train of 3 wheels.. in that case i cant solve it.

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at the speed of 60 rpm and the mixer is mixing at the rate of 8 rpm. What is the diameter of the mixing wheel if the radius of the smaller (drive) wheel is 2 inches?

12 15 25 30 32

I can't image this machine. Could someone explain this or upload the image for me?

Exactly same feeling. Every one will draw their own picture but I could not draw any Totally blanked.

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at the speed of 60 rpm and the mixer is mixing at the rate of 8 rpm. What is the diameter of the mixing wheel if the radius of the smaller (drive) wheel is 2 inches?

12 15 25 30 32

I can't image this machine. Could someone explain this or upload the image for me?

Exactly same feeling. Every one will draw their own picture but I could not draw any Totally blanked.

Same here.. that's why I posted this question.. Can some one picture the problem.. _________________

Your attitude determines your altitude Smiling wins more friends than frowning

Broadly speaking, the ratio of rpm of one wheel to the one directly connected to it is the inverse ratio of the radii.

But from the question, I don't understand which wheel is connected to which. And what does "mixing wheel" or smaller wheel" refer to (smaller than which wheel???)? _________________

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at the speed of 60 rpm and the mixer is mixing at the rate of 8 rpm. What is the diameter of the mixing wheel if the radius of the smaller (drive) wheel is 2 inches?

12 15 25 30 32

mixing @ 8rpm?? did the people who set the verbal paper set this question by mistake? wow!!! probably i can also get a chance to set papers...

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at the speed of 60 rpm and the mixer is mixing at the rate of 8 rpm. What is the diameter of the mixing wheel if the radius of the smaller (drive) wheel is 2 inches?

12 15 25 30 32

engine rate = 60 rpm mixing rate = 8 rpm engine rate/ mixing rate = (2 *pi* r of mixer)/ (2*pi*r of engine) 60/8 = r of mixer / r of engine r of engine>=2 60/8 <= r / 2 r=>15 d = r x 2 d>=30

Justed wanted to post an updated version of the question. Hope it's clearer now.

Quote:

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at a speed of 60 rpm and the mixer is mixing at a rate of 8 rpm. If the radius of the smaller (drive) wheel is 2 inches, what is the diameter of the mixing wheel? The smaller wheel is driven directly by the engine.

The question now makes it clear that the smaller wheel is the drive wheel. I thought the doubts were cleared by adding the "(drive)" part to the question stem. Please tell me what else I can do to make the question clearer.

The question now makes it clear that the smaller wheel is the drive wheel. I thought the doubts were cleared by adding the "(drive)" part to the question stem. Please tell me what else I can do to make the question clearer.

Thanks.

I don't know if it's the same for everyone but definitely I would need it spelled out for me. xxx made up of 3 wheels, the engine, the drive, and the xxx,the small wheel

In other words, I need to know which wheel is which. Just my opinion. Don't know if the same holds for everyone.

Thanks! I'll edit the question if more users find the question confusing. +1.

lagomez wrote:

dzyubam wrote:

The question now makes it clear that the smaller wheel is the drive wheel. I thought the doubts were cleared by adding the "(drive)" part to the question stem. Please tell me what else I can do to make the question clearer.

Thanks.

I don't know if it's the same for everyone but definitely I would need it spelled out for me. xxx made up of 3 wheels, the engine, the drive, and the xxx,the small wheel

In other words, I need to know which wheel is which. Just my opinion. Don't know if the same holds for everyone.

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at the speed of 60 rpm and the mixer is mixing at the rate of 8 rpm. What is the diameter of the mixing wheel if the radius of the smaller (drive) wheel is 2 inches?

12 15 25 30 32

After staring at this problem for several minutes I could not come up with anything, so I tried put myself in the shoes of an evil GMAT question writer and tried to imagine what the answer could be. Notice that the question deals with radii. Radii are often converted into diameters by simply multiplying by two. Since diameters are not mentioned in the question, I guessed that there would be a correct answer and a trap answer based on the knowledge that a diameter is twice the length of the radius. Sure enough, there is a pair of answers that fit: 15 and 15 * 2 = 30. I guessed that 15 was the trap answer and 30 was the correct answer. Whammmy!

...if only I were always so lucky! _________________

This question is terribly confusing. I pictured these three wheels as cogs rotating against one another. Then the ratio (of RPMs) of 60:8 reduces to 15:2. So if the radius of one cog is 2, the radius of the other cog is 15, and the diameter is 30.

I ignored the middle cog. Maybe I lucked out, I'm not sure.