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# 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.

Spoiler:
9

Why?

Last edited by Venusian; 11-17-11 at 05:11 PM. DVD Talk Legend

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Re: Math Question

like the person in the second link, I'm not sure what Z(k,3) even means mathematically. DVD Talk Legend

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Re: Math Question DVD Talk Limited Edition

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Re: Math Question

Dude, you've already got the answer. Who cares why?  DVD Talk Legend

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Re: Math Question

I don't know that language. It's not algebra, that's for sure. DVD Talk Hero

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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. DVD Talk Legend

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Re: Math Question

Must be that new math. DVD Talk Hero

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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. DVD Talk Legend

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Re: Math Question

fuck if I know DVD Talk Godfather

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Re: Math Question "Oh, come on people. It's all vectors these days." Banned

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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?

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. DVD Talk Legend

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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.

Last edited by Nick Danger; 11-17-11 at 10:09 PM. DVD Talk Limited Edition

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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?

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.
The stairs are as long as they are high.

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. DVD Talk Hall of Fame

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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?

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.
No, 66 is correct. It's assuming the cubes have to be supported all the way to the ground. So, 1 step = 1 cube. 2 steps = 3 cubes. 3 steps = 6 cubes. n steps = n(n+1)/2 cubes. 11 steps = 11(12)/2 = 66.

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. DVD Talk Legend

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Re: Math Question

The weird thing is that all the other questions in that practice test are pretty easy.
I don't know about that. I can't solve this one.

Question No 15:
If p + q  r = s, and if p  q + r = t, then a =?  DVD Talk Hall of Fame

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Re: Math Question

I don't know about that. I can't solve this one.

Question No 15:
If p + q  r = s, and if p  q + r = t, then a =?  Yeah, noticed that. I think they wanted to solve for p, based on the available answers. DVD Talk Platinum Edition

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Re: Math Question

Do not try and bend the spoon. That's impossible. Instead... only try to realize the truth. DVD Talk Hero

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Re: Math Question

I wish I was good at math. DVD Talk Hero

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Re: Math Question

Okay, we had half a dozen engineers look at this and no one could figure it out. Now I don't feel so dumb. DVD Talk Hero

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Re: Math Question

No, I don't want to. DVD Talk Ultimate Edition

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Re: Math Question

Can someone help with this:

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

You're welcome. DVD Talk Legend

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