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Robots X, Y, and Z each assemble components at their [#permalink]
03 Jan 2011, 17:30

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Question Stats:

70% (02:13) correct
29% (01:39) wrong based on 198 sessions

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?

Re: Robots X, Y, and Z each assemble [#permalink]
08 Feb 2012, 04:06

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Expert's post

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?

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.

Re: Robots X, Y, and Z each assemble [#permalink]
22 Oct 2013, 07:00

Bunuel wrote:

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?

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.

Answer: C.

Bunuel,

Please help me clarify. The question says "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", so if it is rates, why is X's constant rate not 1/X (which is the rate of completing one unit of work, and Z's rate would therefore be 1/Z. Thus r(x) would be 1/X : 1/Z? What am I misunderstanding here?

Re: Robots X, Y, and Z each assemble [#permalink]
22 Oct 2013, 08:22

Expert's post

bulletpoint wrote:

Bunuel wrote:

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?

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.

Answer: C.

Bunuel,

Please help me clarify. The question says "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", so if it is rates, why is X's constant rate not 1/X (which is the rate of completing one unit of work, and Z's rate would therefore be 1/Z. Thus r(x) would be 1/X : 1/Z? What am I misunderstanding here?

Because we denoted rates by x , y, and z: let the rates of robots X, Y, and Z be x, y, and z respectively. _________________

Re: Robots X, Y, and Z each assemble components at their [#permalink]
03 Nov 2013, 07:25

Hello Everyone, In OG 13, the question uses "rx" and "ry" in the question stem but "r_x (x in suffix)" and "r_y(y in suffix)". Are these typos? Or am I supposed to guess that rx and ry of question stem has been converted to r_x and r_y in the two given options? TIA,

Re: Robots X, Y, and Z each assemble components at their [#permalink]
03 Nov 2013, 10:21

Expert's post

drebellion wrote:

Hello Everyone, In OG 13, the question uses "rx" and "ry" in the question stem but "r_x (x in suffix)" and "r_y(y in suffix)". Are these typos? Or am I supposed to guess that rx and ry of question stem has been converted to r_x and r_y in the two given options? TIA,

It's a typo. x and y must be indexes in both stem and the statements.
_________________

Re: Robots X, Y, and Z each assemble components at their [#permalink]
03 Nov 2013, 11:06

1

This post received KUDOS

Thank you for your reply Bunuel. Also thank you for pointing out the error/typo in Diagnostic Test Q 5 (Cylindrical tank contains 36PI f3 of water...)

At lest for the second question (Cylindrical Tank...) we will never know if its a typo or the guys who had this question in their real GMAT were unfortunate!

Thanks Anyway!

gmatclubot

Re: Robots X, Y, and Z each assemble components at their
[#permalink]
03 Nov 2013, 11:06