GMAT Math

Hi fellows,

2 questions regarding the PROBLEM SOLVING PART of the DIAGNOSTIC TEST IN THE OG 13:

First:

I retook the diagnostic test and tripped over a very easy task in general. Here it is:

A closed cylindrical tank contains 36п cubic feet of water and is filled to half its capacity.

The way i got this task is: that the Cylinder is half full, and, that, when half full it has 36п cubic metres of water in it. Bottom line: 1/2 of the cylinder's Volume is 36п. However, the way it is meant fromthe OG 13 Writers is that the full capacity of the cylinder = 36п and that in addition to that, the cylinder is currently half full.

Since I am not a native speaker I would like to ask you, don't you find the task description a little confusing? If so (and i do not want to make a rush inference) it seems very unprofessional to get such a task on the real exam.


Second:

There is a task where you get this:

A right circular cone is inscribed in a hemisphere so that the base of the cone coincides with the base of the hemisphere. What is the ratio of the height of the cone to the radius of the hemisphere?

Now, I have studied tens of hundreds of pages on Quant topic and there was not a single thing said about a cone or about a hemisphere. Furhtermore I had no clue how to draw a hemisphere, never mind deduce that if the base of the cone coincides with the base of the hemisphere ---> the ration of height of cylinder: radius of the hemisphere = 1:1

Is it possible to get such questions that havent been taught anywhere?

Thank you very much for your answers

For first question even I have my doubts about the intended meaning. My understanding ins 36Pi is the water filled in cylindrical container and cylinder is half filled. Someone can please clarify this doubt.

Now lets take your second doubt.

"Is it possible to get such questions that haven't been taught anywhere?"
Answer is firm no , however, it is possible that something will appear in the exam which you haven't learned or missed. But there will be nothing outside the given topic. Remember one thing, every question will be straightforward or circuitous version of all the reasoning and concepts you've learned.

If you know about sphere you know about Hemi-Sphere(Half sphere).

Imagine a tennis ball cut into two half; each half itself is a hemisphere. Now you can place a cone such that it has same base as that of half cut ball i.e hemisphere.

so the top of cone will touch the boundary of hemisphere.

This figure will make it more clear. This is a 2-d view of hemisphere.

DBushkalov,

On the first question:

"A closed cylindrical tank contains 36п cubic feet of water and is filled to half its capacity."

You are interpreting it correctly. The volume of the water is 36pi and the tank is filled with water to half its capacity, and therefore the tank capacity is 72pi. However, to solve this problem we don't need to go in this direction but your interpretation is correct.

It is possible that you may have the edition of OG 12 that has a typo. You will find the link to the errata on this page:
https://www.gmatquantum.com/og12diagnost ... ition.html

Cheers,
Dabral

dabral wrote:DBushkalov,

On the first question:

It is possible that you may have the edition of OG 12 that has a typo.
Dabral

I've 13th edition and I have found the same problem in this edition too.

First thing... The wording is going to be challenging on a lot of questions. Read slowly. This example says that a container already has 36pi cubic feet in it, and then goes on to say that this is half full. Semantics will be important.

As for the second question, the exam is going to expect you to sort things out on the fly, not simply regurgitate memorized facts. It is tough to think of everything beforehand so you are going to have to simply practice.

Thanks a ton for posting the free video explanations of OG.I'm sure I'll be benefited immensely by these videos.

On the first question:

"A closed cylindrical tank contains 36п cubic feet of water and is filled to half its capacity."

You are interpreting it correctly. The volume of the water is 36pi and the tank is filled with water to half its capacity, and therefore the tank capacity is 72pi. However, to solve this problem we don't need to go in this direction but your interpretation is correct.

It is possible that you may have the edition of OG 12 that has a typo. You will find the link to the errata on this page:
https://www.gmatquantum.com/og12diagnost ... ition.html

Cheers,
Dabral[/quote]