DS - produce x and y

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DS - produce x and y

by Xbond » Sat Aug 29, 2009 7:43 am
Hi there,

Could you explain in the simplest this concept and how to resolve it


If Bob produces 36 or fewer items in a week, he is paid x dollars per item. If Bob produces
more than 36 items in a week, he is paid x dollars per item for the first 36 items and 11/2 times
that amount for each additional item. How many items did Bob produce last week?

(1) Last week Bob was paid a total of $480 for the items that he produced that week.
(2) This week Bob produced 2 items more than last week and was paid a total of $510 for the
items he produced this week.
Source: — Data Sufficiency |

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Re: DS - produce x and y

by Stuart@KaplanGMAT » Sun Aug 30, 2009 7:05 am
Xbond wrote:Hi there,

Could you explain in the simplest this concept and how to resolve it


If Bob produces 36 or fewer items in a week, he is paid x dollars per item. If Bob produces
more than 36 items in a week, he is paid x dollars per item for the first 36 items and 11/2 times
that amount for each additional item. How many items did Bob produce last week?

(1) Last week Bob was paid a total of $480 for the items that he produced that week.
(2) This week Bob produced 2 items more than last week and was paid a total of $510 for the
items he produced this week.
DS is all about methodology. You need to really understand what's going on before jumping in to the statements.

Step 1 of the Kaplan Method for DS: Focus on the Question Stem

Bob has a regular rate and an overtime rate. We know he gets paid $x per item for up to 36 items and 1.5($x) per item for additional items. We need to determine the exact number of items that Bob produced last week.

We can't come up with a simple equation because of the split payment, so let's jump right in to the statements.

Step 2 of the Kaplan Method for DS: Consider each statement by itself.

(1) Since we don't know Bob's rate, there's no way to use this info to figure out how many items he made: insufficient.

(2) Since we don't know Bob's rate, there's no way to use this info to figure out how many items he made: insufficient.

remember: when looking at (2) by itself, we must ignore statement (1) - don't be tempted to use that info too soon!

Step 3 of the Kaplan Method for DS: if necessary, combine the statements.

Neither statement was good enough alone, so here we must combine.

Now we know two things:

-last week Bob made $480
-this week Bob made $510 and made 2 extra items

Therefore, we know that Bob was paid $30 ($510 - $480) for those 2 extra items.

However, do we know if Bob was at his overtime or regular rate? Can we figure out the total number of items?

Now we have to use the most valuable tool for DS: logic and common sense.

Let's work through two scenarios.

First, let's assume that Bob was working at his overtime rate for those two items. If that's the case, then his overtime rate is $15 and his regular rate is $10 (since OT = 1.5 regular).

If that's the case, then could Bob have made $480 the previous week?

Sure, he could have made 36 items at $10 (for $360) and made 8 items at $15 (for the remaining $120).

Second, let's assume that Bob was working at his regular rate for the two items. If that's the case, could Bob have made $480 the previous week?

Sure, he could have made 32 items at $15 (for $480).

Since both scenarios are possible, we still cannot determine exactly how many items Bob made last week: together insufficient, choose (E).
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by goelmohit2002 » Sun Aug 30, 2009 9:07 am
Hi Stuart,

Thanks.

why are we not considering the case#3...i.e. last week she made say 35 items...and this week she made 37...i.e. one over time and one normal case ?

Thanks
Mohit

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by Stuart@KaplanGMAT » Sun Aug 30, 2009 9:34 am
goelmohit2002 wrote:Hi Stuart,

Thanks.

why are we not considering the case#3...i.e. last week she made say 35 items...and this week she made 37...i.e. one over time and one normal case ?

Thanks
Mohit
Hi Mohit,

if we didn't already have multiple answers to the question, we would also consider that case. However, since looking at the two simpler cases gives us two different answers, we already know that the answer is "E".
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by goelmohit2002 » Sun Aug 30, 2009 9:46 am
Stuart Kovinsky wrote:
goelmohit2002 wrote:Hi Stuart,

Thanks.

why are we not considering the case#3...i.e. last week she made say 35 items...and this week she made 37...i.e. one over time and one normal case ?

Thanks
Mohit
Hi Mohit,

if we didn't already have multiple answers to the question, we would also consider that case. However, since looking at the two simpler cases gives us two different answers, we already know that the answer is "E".
oh ok thanks.....!!!

just wanted to confirm that we indeed have to check that case...in case of no ambiguity would have been found..... but since as you said already contradiction exist so we need not verify the same.

Thanks
Mohit

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Re: DS - produce x and y

by pathaniaus » Sun Aug 30, 2009 11:56 am
Mohit or Stuart,

Before I read your explanations, I tried solving it myself, and I got C. And I am still not understanding. Maybe if you guys looked at what I did you can point out what I did wrong and where I am fundamentally wrong.

I chose C because I made simultaneous equations.

Bob gets paid x for the first 36 items and then 11x/2 for every item more than 36.

SO, Pay = 36x + (11x/2)(n-36)

For 1) 36x + (11x/2)(n-36) = 480 (LAST WEEK)
For 2) 36x + (11x/2)((n+2)-36) = 510 (THIS WEEK) Bob made two more items this week than last week so i incorporated that.

Now couldn't you solve the equations since we have two variables and two equations?

Please let me know!

Thanks!

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by crackgmat007 » Sun Aug 30, 2009 1:54 pm
I did in the same way and concluded that it must be C. To make this conlcusion, we assumed that the number of items produced is greater than 36. If the number of items is less than 36, we need to apply normal rate for these 2 additional items. If the number of items is greater than 36, we need to apply overtime rate. Since, we dont have any info of whether the number of items > 36, choose E.