Last visit was: 28 Dec 2024, 09:24 It is currently 28 Dec 2024, 09:24
Decision Tracker
My Rewards
New comers' posts
New posts
Unanswered

Close

GRE Prep Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GRE score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Go to My Error Log Learn more
Close

Request Expert Reply

Confirm Cancel
PREVIOUS TOPIC
NEXT TOPIC

A shipment consists of 1,800 parts, some of which are defect

Tags :
Find Similar Topics  About  Add a Tag

Show Tags
Hide Tags

User avatar
D
Carcass
Verbal Expert
Joined: 18 Apr 2015
Posts: 30526
Own Kudos [?]: 36900 [0]
Given Kudos: 26121
Send PM
A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   24 Jul 2020, 10:54
Expert Reply
00:00

Question Stats:

87% (01:31) correct 12% (01:07) wrong based on 31 sessions

Hide Show timer Statistics

A shipment consists of 1,800 parts, some of which are defective. If a part is chosen from the shipment at random, the probability of it being defective is 1/9 the probability that it is not defective. How many of the parts in the shipment are defective?
(A) 90
(B) 120
(C) 180
(D) 200
(E) 900

Kudos for the right solution and explanation
ShowHide Answer
Official Answer
C
User avatar
G
BrushMyQuant
Moderator
Moderator
Joined: 02 Jan 2020
Status:GRE Quant Tutor
Posts: 1116
Own Kudos [?]: 975 [0]
Given Kudos: 9
Location: India
Concentration: General Management
Schools: XLRI Jamshedpur, India - Class of 2014
GMAT 1: 700 Q51 V31
GPA: 2.8
WE:Engineering (Computer Software)
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   24 Jul 2020, 22:27
1
Let number of defective shipments be x
=> Non defective = Total - defective = 1800 - x

Probability of Picking Defective = \(\frac{Total Defective}{ Total}\) [i.e. = \(\frac{x}{ 1800}\) ]
Probability of Picking Non-Defective = \(\frac{Total Non-Defective}{ Total}\) [i.e. = \(\frac{1800-x}{ 1800}\) ]

\(\frac{Probability Of Picking Defective}{Probability Of Picking Non-Defective}\) = \(\frac{Total Defective}{ Total }\)/ \(\frac{Total Non-Defective}{ Total}\)
= \(\frac{Total Defective}{ Total Non-Defective}\) = \(\frac{x}{ 1800-x}\) = \(\frac{1}{9}\) [ Given]

=> 9x = 1800 - x
=> 10x = 1800
=> x = 180

So, answer will be C
Hope it helps!
User avatar
Farina
Senior Manager
Senior Manager
Joined: 10 Feb 2020
Posts: 496
Own Kudos [?]: 356 [0]
Given Kudos: 299
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 00:13
Is my approach correct?
1/9 * (1-1/9)
1/9*8/9
8/81 = 0.098
0.098 * 1800 = 176.4 approx which is close to 180
User avatar
G
BrushMyQuant
Moderator
Moderator
Joined: 02 Jan 2020
Status:GRE Quant Tutor
Posts: 1116
Own Kudos [?]: 975 [0]
Given Kudos: 9
Location: India
Concentration: General Management
Schools: XLRI Jamshedpur, India - Class of 2014
GMAT 1: 700 Q51 V31
GPA: 2.8
WE:Engineering (Computer Software)
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 00:18
1
Can you elaborate 1/9 * (1-1/9)

Are you saying 1/9 * P(Non-Defective)
So, P(Non-Defective) you are assuming is (1-1/9) that means 1 - P(Defective) = 1 - 1/9
So, you assuming P(Defective) = 1/9 ?
I would not recommend taking that assumption even if the answer is approximately correct.

Hope it helps!
User avatar
Farina
Senior Manager
Senior Manager
Joined: 10 Feb 2020
Posts: 496
Own Kudos [?]: 356 [0]
Given Kudos: 299
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 02:13
BrushMyQuant wrote:
Can you elaborate 1/9 * (1-1/9)

Are you saying 1/9 * P(Non-Defective)
So, P(Non-Defective) you are assuming is (1-1/9) that means 1 - P(Defective) = 1 - 1/9
So, you assuming P(Defective) = 1/9 ?
I would not recommend taking that assumption even if the answer is approximately correct.

Hope it helps!


The question stem says:
The probability of it being defective is 1/9 the probability that it is not defective

being defective: 1/9
of the probability being non defective: Non defective would be 1-1/9

so if you translate Eng into Maths: The probability of it being defective is 1/9 the probability that it is not defective
: 1/9 * (1-1/9)

or maybe I have not understood it correctly
User avatar
G
BrushMyQuant
Moderator
Moderator
Joined: 02 Jan 2020
Status:GRE Quant Tutor
Posts: 1116
Own Kudos [?]: 975 [0]
Given Kudos: 9
Location: India
Concentration: General Management
Schools: XLRI Jamshedpur, India - Class of 2014
GMAT 1: 700 Q51 V31
GPA: 2.8
WE:Engineering (Computer Software)
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 03:08
@Farina

I get confusion now. The question says "the probability of it being defective is 1/9 the probability that it is not defective"

They actually wanted to say that "the probability of it being defective is 1/9th of the probability that it is not defective"

@Carcass: Do we want to edit the question to have this specified please?

Hope it helps!
User avatar
D
Carcass
Verbal Expert
Joined: 18 Apr 2015
Posts: 30526
Own Kudos [?]: 36900 [0]
Given Kudos: 26121
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 03:13
Expert Reply
Sorry Guys

I should add the cardinal th ??

Is it this ?' But the question is correct as is transcribed ??

Will see what @GreenlightTestPrep says
User avatar
Farina
Senior Manager
Senior Manager
Joined: 10 Feb 2020
Posts: 496
Own Kudos [?]: 356 [0]
Given Kudos: 299
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 05:01
BrushMyQuant wrote:
@Farina

I get confusion now. The question says "the probability of it being defective is 1/9 the probability that it is not defective"

They actually wanted to say that "the probability of it being defective is 1/9th of the probability that it is not defective"

@Carcass: Do we want to edit the question to have this specified please?

Hope it helps!


If you would add "of" my solution would be correct I think :) Hence the confusion remains
User avatar
G
BrushMyQuant
Moderator
Moderator
Joined: 02 Jan 2020
Status:GRE Quant Tutor
Posts: 1116
Own Kudos [?]: 975 [0]
Given Kudos: 9
Location: India
Concentration: General Management
Schools: XLRI Jamshedpur, India - Class of 2014
GMAT 1: 700 Q51 V31
GPA: 2.8
WE:Engineering (Computer Software)
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 06:06
1
"the probability of it being defective is 1/9th of the probability that it is not defective"
This does not mean that Probability of Defective is 1/9
This means that probability of defective = 1/9th of the probability of non-Defective

Ex: If probability of non-defective is 9/10 then probability of defective is 1/9 of 9/10 = 1/10

Hope it helps!
User avatar
Farina
Senior Manager
Senior Manager
Joined: 10 Feb 2020
Posts: 496
Own Kudos [?]: 356 [0]
Given Kudos: 299
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 06:09
BrushMyQuant wrote:
"the probability of it being defective is 1/9th of the probability that it is not defective"
This doe not mean that Probability of Defective is 1/9
This means that probability of defective = 1/9th of the probability of non-Defective

Ex: If probability of non-defective is 9/10 then probability of defective is 1/9 of 9/10 = 1/10

Hope it helps!

I got it now, thanks a lot for your help. It was certainly the problem of my understanding of language
User avatar
D
Carcass
Verbal Expert
Joined: 18 Apr 2015
Posts: 30526
Own Kudos [?]: 36900 [0]
Given Kudos: 26121
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 06:17
Expert Reply
To be honest I did not get the point to edit the question because for me there was nothing wrong in the wording :|
User avatar
G
BrushMyQuant
Moderator
Moderator
Joined: 02 Jan 2020
Status:GRE Quant Tutor
Posts: 1116
Own Kudos [?]: 975 [0]
Given Kudos: 9
Location: India
Concentration: General Management
Schools: XLRI Jamshedpur, India - Class of 2014
GMAT 1: 700 Q51 V31
GPA: 2.8
WE:Engineering (Computer Software)
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 06:52
Now that I re-read it and re-re-re-read it then it sounds okay I guess
User avatar
P
GreenlightTestPrep
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12239 [0]
Given Kudos: 136
Send PM

Top Member of the Month
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 07:26
3
Carcass wrote:
A shipment consists of 1,800 parts, some of which are defective. If a part is chosen from the shipment at random, the probability of it being defective is 1/9 the probability that it is not defective. How many of the parts in the shipment are defective?
(A) 90
(B) 120
(C) 180
(D) 200
(E) 900


The probability of it (the part) being defective is 1/9 the probability that it is not defective
This does NOT mean P(getting a defective part) = 1/9

Let x = the probability that the part is defective
So, 1 - x = the probability that the part is NOT defective

From the given information we can write: (probability of defective part) = (1/9)(probability of NON-defective part)
So we can write: x = (1/9)(1 - x)
To eliminate the fractions, multiply both sides by 9 to get: 9x = 1 - x
Add x to both sides: 10x = 1
Divide both sides by 10 to get: x = 1/10

So, P(electing a defective part) = 1/10
In other words, 1/10 of all parts are defective.

If there are 1800 parts in total, then the number of defective parts = 1/10 of 1800 = 180

Answer: C

Cheers,
Brent
User avatar
D
Carcass
Verbal Expert
Joined: 18 Apr 2015
Posts: 30526
Own Kudos [?]: 36900 [0]
Given Kudos: 26121
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 08:43
Expert Reply
BrushMyQuant wrote:
Now that I re-read it and re-re-re-read it then it sounds okay I guess


Exactly
User avatar
D
Carcass
Verbal Expert
Joined: 18 Apr 2015
Posts: 30526
Own Kudos [?]: 36900 [0]
Given Kudos: 26121
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 08:44
Expert Reply
GreenlightTestPrep wrote:
Carcass wrote:
A shipment consists of 1,800 parts, some of which are defective. If a part is chosen from the shipment at random, the probability of it being defective is 1/9 the probability that it is not defective. How many of the parts in the shipment are defective?
(A) 90
(B) 120
(C) 180
(D) 200
(E) 900


The probability of it (the part) being defective is 1/9 the probability that it is not defective
This does NOT mean P(getting a defective part) = 1/9

Let x = the probability that the part is defective
So, 1 - x = the probability that the part is NOT defective

From the given information we can write: (probability of defective part) = (1/9)(probability of NON-defective part)
So we can write: x = (1/9)(1 - x)
To eliminate the fractions, multiply both sides by 9 to get: 9x = 1 - x
Add x to both sides: 10x = 1
Divide both sides by 10 to get: x = 1/10

So, P(electing a defective part) = 1/10
In other words, 1/10 of all parts are defective.

If there are 1800 parts in total, then the number of defective parts = 1/10 of 1800 = 180

Answer: C

Cheers,
Brent



Thank you Sir for the explanation
User avatar
P
GreenlightTestPrep
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12239 [0]
Given Kudos: 136
Send PM

Top Member of the Month
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   25 Jul 2020, 09:06
Farina wrote:
Is my approach correct?
1/9 * (1-1/9)
1/9*8/9
8/81 = 0.098
0.098 * 1800 = 176.4 approx which is close to 180


Yes, 176.4 is close to 180, but the question isn't asking us to find the "approximate" number of defective parts.

In your solution, what does "1/9*8/9" represent?
User avatar
Farina
Senior Manager
Senior Manager
Joined: 10 Feb 2020
Posts: 496
Own Kudos [?]: 356 [0]
Given Kudos: 299
Send PM
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink] New post   26 Jul 2020, 00:45
GreenlightTestPrep wrote:
Farina wrote:
Is my approach correct?
1/9 * (1-1/9)
1/9*8/9
8/81 = 0.098
0.098 * 1800 = 176.4 approx which is close to 180


Yes, 176.4 is close to 180, but the question isn't asking us to find the "approximate" number of defective parts.

In your solution, what does "1/9*8/9" represent?


I considered 1/9 as defective and 1-1/9 as non defective. You have already addressed in your answer that this assumption is wrong.
Prep Club for GRE Bot
gmatclubot
Re: A shipment consists of 1,800 parts, some of which are defect [#permalink]
26 Jul 2020, 00:45
Moderators:
adewale223
GRE Instructor
88 posts
bronaugust
GRE Forum Moderator
37 posts
BrushMyQuant
Moderator
1116 posts
VibhuAnurag
GRE Instructor
234 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Main navigation

Partners

GRE Resources

www.ets.org/gre | About | Terms and Conditions and Privacy Policy | Prep Club for GRE Rules | Contact