# Math Question

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**Math Question**

Can someone help with this:

http://www.grepracticetest.org/pract...estion-19.html

If Z(k-1,3) : Z(k,3) = 1:9, find k.

The answer is:

Why?

Does this help? http://answers.yahoo.com/question/in...5093558AAft0FA

http://www.grepracticetest.org/pract...estion-19.html

If Z(k-1,3) : Z(k,3) = 1:9, find k.

The answer is:

**Spoiler:**

Why?

Does this help? http://answers.yahoo.com/question/in...5093558AAft0FA

*Last edited by Venusian; 11-17-11 at 05:11 PM.*

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**6**DVD Talk Hero

**Re: Math Question**

It makes no sense to me. They're saying ther'es a function Z in which you plug in two numbers. If you plug in k-1 and 3, you get answer A and if you plug in k and 3, you get answer B. The ratio of A to B is 1 to 9, and from that, they determine that the answer is that k must be 9. And that is certainly true if the function is Z(x,y) = (2x-15)^(y-1). But if the function is Z(x,y) = 8x+y-2, then k has to equal 1. And we could come up with all sorts of other equations that give a 1:9 ratio for various values of k.

So basically, I'm no help whatsoever in answering Venusian's question.

So basically, I'm no help whatsoever in answering Venusian's question.

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**Re: Math Question**

What if Z is a two dimensional matrix.

The whole question has no meaning unless there is more definition of what Z means, and were weren't given that part of the question.

The whole question has no meaning unless there is more definition of what Z means, and were weren't given that part of the question.

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**Re: Math Question**

Here's an unrelated math question. On this week's episode of Parenthood, Max answered this math question:

If 6 ice cubes could build stairs of 3 steps, then how many ice cubes would it take to build stairs of 11 steps?

Max answered 66.

Shouldn't it be 22? 6x(11/3) = 22. Apparently Max just took 6x11.

The show tries to make him look like such a math genius, but that question was so simple and he missed it by a long shot that it really stood out.

If 6 ice cubes could build stairs of 3 steps, then how many ice cubes would it take to build stairs of 11 steps?

Max answered 66.

Shouldn't it be 22? 6x(11/3) = 22. Apparently Max just took 6x11.

The show tries to make him look like such a math genius, but that question was so simple and he missed it by a long shot that it really stood out.

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**12**DVD Talk Legend

**Re: Math Question**

Am I misunderstanding the second link? It's been a long time since high school math.

If it's a permutation, it doesn't work as stated in the link.

P(9,3) = 9x8x7.

P(8,3) = 8x7x6.

The ratio is 6:9, which is not 1:9.

If it's a combination, it still doesn't work.

C(9,3) = (9x8x7)/3! = (9x8x7)/6

C(8,3) = (8x7x6)/3! = (8x7x6)/6

The ratio is 6/6 : 9/6 which still isn't 1:9.

If it's a permutation, it doesn't work as stated in the link.

P(9,3) = 9x8x7.

P(8,3) = 8x7x6.

The ratio is 6:9, which is not 1:9.

If it's a combination, it still doesn't work.

C(9,3) = (9x8x7)/3! = (9x8x7)/6

C(8,3) = (8x7x6)/3! = (8x7x6)/6

The ratio is 6/6 : 9/6 which still isn't 1:9.

*Last edited by Nick Danger; 11-17-11 at 10:09 PM.*

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**Re: Math Question**

If 6 ice cubes could build stairs of 3 steps, then how many ice cubes would it take to build stairs of 11 steps?

Max answered 66.

Shouldn't it be 22? 6x(11/3) = 22. Apparently Max just took 6x11.

The show tries to make him look like such a math genius, but that question was so simple and he missed it by a long shot that it really stood out.

That means for every step, the number of ice cubes to make that step decreases by 1.

So for steps 3 cubes high, it's (3+2+1) = 6 cubes.

For steps 11 cubes high, it's (11+10+9...+1) = 66.

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**Re: Math Question**

If 6 ice cubes could build stairs of 3 steps, then how many ice cubes would it take to build stairs of 11 steps?

Max answered 66.

Shouldn't it be 22? 6x(11/3) = 22. Apparently Max just took 6x11.

The show tries to make him look like such a math genius, but that question was so simple and he missed it by a long shot that it really stood out.

re: the original posters question, I came to the same conclusion as everyone else. Never heard of Z(x,y) notation, and have no idea what it means. Even considered the combination/permutation hinted at in the other link, and found, as Nick Danger, that it didn't work.

The weird thing is that all the other questions in that practice test are pretty easy.

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