GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 22 Feb 2019, 12:36

### GMAT 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

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

Practice
Pays

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

## Events & Promotions

###### Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
• ### Free GMAT RC Webinar

February 23, 2019

February 23, 2019

07:00 AM PST

09:00 AM PST

Learn reading strategies that can help even non-voracious reader to master GMAT RC. Saturday, February 23rd at 7 AM PT
• ### FREE Quant Workshop by e-GMAT!

February 24, 2019

February 24, 2019

07:00 AM PST

09:00 AM PST

Get personalized insights on how to achieve your Target Quant Score.

# Three of 12 remote controls in a box are defective. The remote control

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 53066
Three of 12 remote controls in a box are defective. The remote control  [#permalink]

### Show Tags

29 Mar 2018, 22:54
00:00

Difficulty:

25% (medium)

Question Stats:

80% (01:20) correct 20% (01:59) wrong based on 70 sessions

### HideShow timer Statistics

Three of 12 remote controls in a box are defective. The remote controls are tested one at a time and not replaced in the box after testing. What is the probability that neither of the first two remote controls tested is defective?

(A) 1/6
(B) 2/9
(C) 6/11
(D) 9/16
(E) 3/4

_________________
BSchool Forum Moderator
Joined: 07 Jan 2016
Posts: 938
Location: India
GMAT 1: 710 Q49 V36
Re: Three of 12 remote controls in a box are defective. The remote control  [#permalink]

### Show Tags

29 Mar 2018, 22:59
Bunuel wrote:
Three of 12 remote controls in a box are defective. The remote controls are tested one at a time and not replaced in the box after testing. What is the probability that neither of the first two remote controls tested is defective?

(A) 1/6
(B) 2/9
(C) 6/11
(D) 9/16
(E) 3/4

3 defective
12 total
9 non defective

neither of first two defective = 9/12 x 8/11 = 6/11
Manager
Joined: 05 Feb 2016
Posts: 157
Location: India
Concentration: General Management, Marketing
WE: Information Technology (Computer Software)
Re: Three of 12 remote controls in a box are defective. The remote control  [#permalink]

### Show Tags

29 Mar 2018, 23:38
3 defective
12 total
9 non defective

neither of first two defective = 9/12 x 9/12(since not replaced) = 9/16
Intern
Joined: 18 Mar 2018
Posts: 2
Re: Three of 12 remote controls in a box are defective. The remote control  [#permalink]

### Show Tags

30 Mar 2018, 00:38
kunalcvrce wrote:
3 defective
12 total
9 non defective

neither of first two defective = 9/12 x 9/12(since not replaced) = 9/16

„Not replaced“ means that in the second choice you only have 11 left to choose from, doesn’t it?

Hence -> 6/11
BSchool Forum Moderator
Joined: 07 Jan 2016
Posts: 938
Location: India
GMAT 1: 710 Q49 V36
Re: Three of 12 remote controls in a box are defective. The remote control  [#permalink]

### Show Tags

30 Mar 2018, 00:41
kunalcvrce wrote:
3 defective
12 total
9 non defective

neither of first two defective = 9/12 x 9/12(since not replaced) = 9/16

9/12 now 1 ball is removed

8/11

this becomes the new fraction 6/11 would be the answer IMO
Manager
Joined: 05 Feb 2016
Posts: 157
Location: India
Concentration: General Management, Marketing
WE: Information Technology (Computer Software)
Re: Three of 12 remote controls in a box are defective. The remote control  [#permalink]

### Show Tags

30 Mar 2018, 00:53
JaBre wrote:
kunalcvrce wrote:
3 defective
12 total
9 non defective

neither of first two defective = 9/12 x 9/12(since not replaced) = 9/16

„Not replaced“ means that in the second choice you only have 11 left to choose from, doesn’t it?

Hence -> 6/11

Correct my mistake..Thanks
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 4955
Location: United States (CA)
Re: Three of 12 remote controls in a box are defective. The remote control  [#permalink]

### Show Tags

04 Apr 2018, 16:30
Bunuel wrote:
Three of 12 remote controls in a box are defective. The remote controls are tested one at a time and not replaced in the box after testing. What is the probability that neither of the first two remote controls tested is defective?

(A) 1/6
(B) 2/9
(C) 6/11
(D) 9/16
(E) 3/4

Since there are 9 non-defective remotes out of 12 in the box, the probability that the first remote selected is not defective is 9/12, or 3/4. We don’t put the first selected remote control back in the box. Thus, there are now 11 remotes in the box, and 8 of them are not defective. Thus, the probability that the second remote control is not defective is 8/11.

Thus, the probability that the first two remote controls are not defective is 9/12 x 8/11 = 3/4 x 8/11 = 24/44 = 6/11.

_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: Three of 12 remote controls in a box are defective. The remote control   [#permalink] 04 Apr 2018, 16:30
Display posts from previous: Sort by