Bob GMATPrep Problem

Expert replies

student22: Master | Next Rank: 500 Posts; Posts: 216; Joined: Mon Dec 21, 2009 10:26 am; Thanked: 16 times

by student22 » Tue Apr 27, 2010 8:05 am

This problem was touched upon before on this forum, but very briefly. Can someone please explain where my work went wrong?

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 1.5 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 that he produced this week.

OA: E

I chose C, and this is what I did:

Let n = number of items

From statement 1:
xn + 1.5x(n - 36) = 480 --> 2.5xn - 54x = 480

From statement 2:
I only subtracted 34, since he produced 2 more items.
xn + 1.5x(n - 34) = 510 --> 2.5xn - 51x = 510 --> xn = .4(510 + 51x)

Now combined:
2.5(.4(510 + 51x) - 54x = 480 --> solve for x. And then you can solve for n.

What did I do wrong?

Like this post

Source: Beat The GMAT — Data Sufficiency | Tue Apr 27, 2010 8:05 am

rockeyb: Legendary Member; Posts: 537; Joined: Sun Jul 19, 2009 7:15 amFollowed by: 1 member; Location: Nagpur , India; Thanked: 41 times

by rockeyb » Tue Apr 27, 2010 8:58 am

student22 wrote:This problem was touched upon before on this forum, but very briefly. Can someone please explain where my work went wrong?

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 1.5 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 that he produced this week.

OA: E

I chose C, and this is what I did:

Let n = number of items

From statement 1:
xn + 1.5x(n - 36) = 480 --> 2.5xn - 54x = 480

From statement 2:
I only subtracted 34, since he produced 2 more items.
xn + 1.5x(n - 34) = 510 --> 2.5xn - 51x = 510 --> xn = .4(510 + 51x)

What did I do wrong?

This is where you went wrong twice in statement 1 and 2 . Do you know for sure that the items produced are more than 36 in each occasion.

"Know thyself" and "Nothing in excess"

Like this post

iamseer: Master | Next Rank: 500 Posts; Posts: 170; Joined: Wed Jun 10, 2009 5:59 am; Thanked: 13 times

by iamseer » Tue Apr 27, 2010 9:05 am

Vow!! this was a good one.

First your minor errors marked in green in quoted text.

Let n = number of items

From statement 1:
36x + 1.5x(n - 36) = 480

From statement 2:
I only subtracted 34, since he produced 2 more items.
36x + 1.5x(n - 34) = 510

So these are 2 equations in 2 unknowns and hence the obvious is C. x=10, n=44
But wait.

We are asked what is the the number of items produced? And in the above quoted text we are assuming that the number is greater than 36. But he can very well produce less than 36 in which case equations would be
from 1: nx=480
from 2: (n+2)x=510
therefore 2x=30, so x=15, n=32

So even after combining 2 statements we get two valid values for n.

Therefore both statements are together INSUFFICIENT.
Hence E.

HTH

"Choose to chance the rapids and dance the tides"

Like this post

student22: Master | Next Rank: 500 Posts; Posts: 216; Joined: Mon Dec 21, 2009 10:26 am; Thanked: 16 times

by student22 » Tue Apr 27, 2010 10:38 am

Ah, good call guys. You're right I assumed (without reason) that there would be at least 36.

But, since we can't assume that here, as iamseer pointed out, it makes sense that it's E.

Thanks!

Like this post

arora007: Community Manager; Posts: 1048; Joined: Mon Aug 17, 2009 3:26 amFollowed by: 27 members; Location: India; Thanked: 51 times; GMAT Score:670

by arora007 » Sun Feb 20, 2011 5:31 am

perfect trap... fortunately I did not step it!

https://www.skiponemeal.org/
https://twitter.com/skiponemeal
Few things are impossible to diligence & skill.Great works are performed not by strength,but by perseverance

pm me if you find junk/spam/abusive language, Lets keep our community clean!!

Like this post

ankurmit: Legendary Member; Posts: 516; Joined: Mon Nov 02, 2009 6:42 amFollowed by: 1 member; Location: Mumbai; Thanked: 14 times; GMAT Score:710

by ankurmit » Wed Feb 23, 2011 4:19 am

Unfortunately I stepped in

Nice quistion

--------
Ankur mittal

Like this post

cyrwr1: Master | Next Rank: 500 Posts; Posts: 218; Joined: Sat Jul 24, 2010 2:43 pm; Thanked: 5 times

by cyrwr1 » Wed Mar 02, 2011 1:47 pm

Are the quantities of 32 and 34 respectively, the only options?

Like this post

Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

by Night reader » Wed Mar 02, 2011 2:31 pm

given and find the number of items produced last week, y-?
st(1) Insufficient, as we have no clue about the number of items produced last week;
st(2) Insufficient, as we have no clue about the number of items produced this week and may not deduct the number of items produced last week;
Combined st(1&2) (510-480)/(y-2)= {x or 1.5x} we cannot solve for y, as we need to define x or 1.5x? Not Sufficient.

answer E, where's the trick here?

student22 wrote:This problem was touched upon before on this forum, but very briefly. Can someone please explain where my work went wrong?

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 1.5 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 that he produced this week.

OA: E

I chose C, and this is what I did:

Let n = number of items

From statement 1:
xn + 1.5x(n - 36) = 480 --> 2.5xn - 54x = 480

From statement 2:
I only subtracted 34, since he produced 2 more items.
xn + 1.5x(n - 34) = 510 --> 2.5xn - 51x = 510 --> xn = .4(510 + 51x)

Now combined:
2.5(.4(510 + 51x) - 54x = 480 --> solve for x. And then you can solve for n.

What did I do wrong?

My knowledge frontiers came to evolve the GMATPill's methods - the credited study means to boost the Verbal competence. I really like their videos, especially for RC, CR and SC. You do check their study methods at https://www.gmatpill.com

Like this post

ankurmit: Legendary Member; Posts: 516; Joined: Mon Nov 02, 2009 6:42 amFollowed by: 1 member; Location: Mumbai; Thanked: 14 times; GMAT Score:710

by ankurmit » Thu Mar 03, 2011 6:35 am

I dont know where you messed up but

we get this equation

From statement 1:
36x + 1.5x(n - 36) = 480

From statement 2:
I only subtracted 34, since he produced 2 more items.
36x + 1.5x(n - 34) = 510

There are 2 equations and 2 variables and we can find them.

But this is not the only case :

We are asked what is the the number of items produced? And in the above quoted text we are assuming that the number is greater than 36. But he can very well produce less than 36 in which case equations would be
from 1: nx=480
from 2: (n+2)x=510
therefore 2x=30, so x=15, n=32

Hence answer is E.

Hope you understand it

--------
Ankur mittal

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review