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Senior Manager  Joined: 30 Nov 2008
Posts: 407
Schools: Fuqua
Robots X, Y, and Z each assemble components at their  [#permalink]

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3
9 00:00

Difficulty:   25% (medium)

Question Stats: 75% (01:45) correct 25% (01:47) wrong based on 515 sessions

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Robots X, Y, and Z each assemble components at their respective constant rates. If $$r_x$$ is the ratio of Robot X's constant rate to Robot Z's constant rate and $$r_y$$ is the ratio of Robot Y's constant rate to Robot Z's constant rate, is Robot Z's constant rate the greatest of the three?

(1) $$r_x < r_y$$
(2) $$r_y < 1$$

OPEN DISCUSSION OF THIS QUESTION IS HERE: http://gmatclub.com/forum/robots-x-y-an ... 39477.html
Manager  Joined: 19 Aug 2006
Posts: 158
Re: Robots X, Y, and Z each assemble components at their  [#permalink]

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stmnt 1 - not suffic.
a<b => x/z < y/z => x< y

stmnt 2 - b<1 - not suffic.

let's combine - b<1 => a<b and a<1
still not sufficient, z could be >,= or < than a and/or b, and it would still satisfy stmnt 1 and 2.

I think it's E.
Intern  Joined: 30 Oct 2008
Posts: 24
Re: Robots X, Y, and Z each assemble components at their  [#permalink]

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for 1 and 2
a < b < 1
x/z < y/z < 1
denominator z is greater than numerator. Hence C is answer.
Director  Joined: 04 Jan 2008
Posts: 626
Re: Robots X, Y, and Z each assemble components at their  [#permalink]

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I think E
Lets take V as Robot Z's constant rate

is Robot Z's constant rate the greatest of the three?

X:Y:Z=Va:Vb:V
now to have V highest we need to know whether V is <0 or >0
V could be 2 or say, 1/2
it changes the whole picture

Robots X, Y, and Z each assemble components in their respective constant rates. If a is the ration of Robot X's constant rate to Robot Z's constant rate and b is the ratio of Robot Y's constant rate to Robot Z's constant rate, is Robot Z's constant rate the greatest of the three.
1) a < b
2) b < 1
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Current Student Joined: 13 Jan 2009
Posts: 258
Location: India
Re: Robots X, Y, and Z each assemble components at their  [#permalink]

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My take is C

X:Z=a; Y:Z=b
that means Z is bigger than Y.

1 says a<b so again Z is bigger than X.

Lets solve it by statements

Y= bZ Y is b times faster than Z if b is less than 1 then Z is faster on the similar note A can deduced.

@A Nitya .... Picture will not change as long as V is greater zero and V can not be negative as rate will always be positive.
Manager  Joined: 19 Aug 2006
Posts: 158
Re: Robots X, Y, and Z each assemble components at their  [#permalink]

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hemantsood wrote:
My take is C

X:Z=a; Y:Z=b
that means Z is bigger than Y.

1 says a<b so again Z is bigger than X.

Lets solve it by statements

Y= bZ Y is b times faster than Z if b is less than 1 then Z is faster on the similar note A can deduced.

@A Nitya .... Picture will not change as long as V is greater zero and V can not be negative as rate will always be positive.

I think you reasoning is correct, the answer should be C, not E.
Manager  Joined: 13 Aug 2010
Posts: 120
Re: Robots X, Y, and Z each assemble components at their  [#permalink]

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1
We need both the information if the constant rate for Z is greater or not.
1. says that constant rate of Y is greater than X. x/z < x/y
2. says that constant rate of Y is smaller than Z. y/z <1

so we need both the information.
Math Expert V
Joined: 02 Sep 2009
Posts: 59020
Re: Robots X, Y, and Z each assemble components at their  [#permalink]

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3
1
ajit257 wrote:
see attachment

Can some explain the reasoning behind this ques.

Robots X, Y, and Z each assemble components at their respective constant rates. If rx is the ratio of robot X's constant rate to robot Z's constant rate and ry is the ratio of robot Y's constant rate to robot Z's constant rate, is robot Z's constant rate the greatest of the three?

Let the rates of robots X, Y, and Z be x, y, and z respectively. Given: $$r_x=\frac{x}{z}$$ and $$r_y=\frac{y}{z}$$. Question is $$z>x$$ and $$z>y$$?

(1) $$r_x<r_y$$ --> $$\frac{x}{z}<\frac{y}{z}$$ --> $$x<y$$. Not sufficient.

(2) $$r_y<1$$ --> $$\frac{y}{z}<1$$ --> $$y<z$$. Not sufficient.

(1)+(2) As $$x<y$$ and $$y<z$$ then $$x<y<z$$. Sufficient.

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Math Expert V
Joined: 02 Sep 2009
Posts: 59020
Re: Robots X, Y, and Z each assemble components at their  [#permalink]

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

Robots X, Y, and Z each assemble components at their respective constant rates. If $$r_x$$ is the ratio of Robot X's constant rate to Robot Z's constant rate and $$r_y$$ is the ratio of Robot Y's constant rate to Robot Z's constant rate, is Robot Z's constant rate the greatest of the three?

(1) $$r_x < r_y$$
(2) $$r_y < 1$$

OPEN DISCUSSION OF THIS QUESTION IS HERE: robots-x-y-and-z-each-assemble-components-at-their-respect-139477.html
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Non-Human User Joined: 09 Sep 2013
Posts: 13568
Re: Robots X, Y, and Z each assemble components at their  [#permalink]

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_________________ Re: Robots X, Y, and Z each assemble components at their   [#permalink] 25 Feb 2017, 16:16
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