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

 It is currently 21 Oct 2018, 08:01

### 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

# A shipment of 500 bulbs contains 10% defective bulbs. If three

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Senior PS Moderator
Joined: 26 Feb 2016
Posts: 3190
Location: India
GPA: 3.12
A shipment of 500 bulbs contains 10% defective bulbs. If three  [#permalink]

### Show Tags

16 Mar 2018, 09:51
1
3
00:00

Difficulty:

95% (hard)

Question Stats:

39% (02:57) correct 61% (02:57) wrong based on 45 sessions

### HideShow timer Statistics

A shipment of 500 bulbs contains 10% defective bulbs. If three bulbs are chosen
randomly, what is the probability that exactly 2 of them are defective?

A. $$\frac{1}{500}$$
B. $$\frac{3}{500}$$
C. $$\frac{3}{1000}$$
D. $$\frac{9}{1000}$$
E. $$\frac{27}{1000}$$

Source: Experts Global

_________________

You've got what it takes, but it will take everything you've got

Manager
Joined: 28 Jan 2018
Posts: 54
Location: Netherlands
Concentration: Finance
GMAT 1: 710 Q50 V36
GPA: 3
A shipment of 500 bulbs contains 10% defective bulbs. If three  [#permalink]

### Show Tags

16 Mar 2018, 12:15
Since the number of bulb is too big, i have to use approximation to arrive to the conclusion

Probability that exactly 2 bulb will be broken: 50/500 * 49/499 * 448/498 = 0.1 * 0.1 * 0.9 = 0.009

Since 2 broken light bulb can be arrange in 3!/2! way, the final answer will be: 0.09 * 3 = 0.027 => Answer E
Senior Manager
Joined: 31 Jul 2017
Posts: 477
Location: Malaysia
Schools: INSEAD Jan '19
GMAT 1: 700 Q50 V33
GPA: 3.95
WE: Consulting (Energy and Utilities)
Re: A shipment of 500 bulbs contains 10% defective bulbs. If three  [#permalink]

### Show Tags

18 Mar 2018, 07:45
pushpitkc wrote:
A shipment of 500 bulbs contains 10% defective bulbs. If three bulbs are chosen
randomly, what is the probability that exactly 2 of them are defective?

A. $$\frac{1}{500}$$
B. $$\frac{3}{500}$$
C. $$\frac{3}{1000}$$
D. $$\frac{9}{1000}$$
E. $$\frac{27}{1000}$$

Source: Experts Global

Number of Defective Bulbs = 50
Number of Non-Defective Bulbs = 450
Ways of Selecting Exactly 2 Ddefective Bulbs & 1 non-Defective Bulb
= $$50C2 * 450C1$$
Total Number of Ways = $$500C3.$$

Probability = $$50C2 * 450C1 / 500C3.$$ = 0.027
_________________

If my Post helps you in Gaining Knowledge, Help me with KUDOS.. !!

Intern
Joined: 27 May 2015
Posts: 7
Schools: ISB '18
Re: A shipment of 500 bulbs contains 10% defective bulbs. If three  [#permalink]

### Show Tags

29 Mar 2018, 07:25
Probability of bulb being defective: 1/10
Probability of bulb being non- defective: 1-1/10=9/10
No. of ways of choosing 2 Defective and one Non Defective Bulb: 3!/2!=3
Probability required: 3*(1/10)*(1/10)*(9/10)=27/1000
Re: A shipment of 500 bulbs contains 10% defective bulbs. If three &nbs [#permalink] 29 Mar 2018, 07:25
Display posts from previous: Sort by

# A shipment of 500 bulbs contains 10% defective bulbs. If three

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.