BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

★★★★★5.0559 reviews
GMATLiveTeach 7 seats left
Chris Peckover
NEXT LIVE COHORT

Oct 13 to Jan 7, 2027

with Chris Peckover

Schedule
Tue, Thu · 8:00 to 10:00 PM ET
Included
40 live hours + 6 months of GMAT OnDemand
  • Live instruction and real-time questions
  • Class recordings and assigned practice
View class & enroll
Limited cohort · enrollment openTarget Test Prep
EALiveTeach 5 seats left
Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
Live EA class + 6 months of EA OnDemand
  • Expert-led weekly online sessions
  • EA Masterclass access between classes
View EA class & enroll
Limited cohort · enrollment openTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

130-point score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

String of lightbulbs

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 75
Joined: Fri Jan 16, 2009 2:00 pm
Thanked: 1 times
GMAT Score:550
by jfranco23 » Tue Mar 17, 2009 5:06 pm
A string of lightbulbs is wired in such a way that if any individual lightbulb fails, the entire string fails. If for each individual lightbulb the probability of failing during time period T is 0.06, what is the probability that the string of lightbulbs will fail during time period T?

A. 0.06
B. (0.06)^10
C. 1 - (0.06)^10
D. (0.94)^10
E. 1 - (0.94)^10
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 246
Joined: Mon May 19, 2008 7:34 am
Location: Texaco Gas Station
Thanked: 7 times

by cubicle_bound_misfit » Wed Mar 18, 2009 7:52 am
whats the no of lightbulbs in the string?
Cubicle Bound Misfit
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 77
Joined: Sun Feb 22, 2009 5:51 am
Thanked: 1 times

by rseeker2 » Wed Mar 18, 2009 8:49 am
probability that the string of lightbulbs will fail during time period T --> 1-P(no bulb failing)

= 1 - (0.94)^n

If n were 10, it would be 1 - (0.94)^10
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members
Location: Toronto
Thanked: 1710 times
GMAT Score:800

by Stuart@KaplanGMAT » Wed Mar 18, 2009 11:00 am
rseeker2 wrote:probability that the string of lightbulbs will fail during time period T --> 1-P(no bulb failing)

= 1 - (0.94)^n

If n were 10, it would be 1 - (0.94)^10
Perfect!

Based on the answer choices, there must be 10 lightbulbs - the OP must have missed part of the question (maybe it really started with "A string of 10 lightbulbs...").
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 75
Joined: Fri Jan 16, 2009 2:00 pm
Thanked: 1 times
GMAT Score:550

by jfranco23 » Wed Mar 18, 2009 11:58 am
So sorry for my mistake, there are 10 lightbulbs.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Sun Feb 22, 2009 11:27 pm
GMAT Score:600

by hijazim » Thu Mar 19, 2009 7:09 am
Shouldn't it be (0.06)x10 because it is OR not AND probability. As if any of the lightbulbs failed the whole string will fail, so if the 1st or 2nd or ... 10th fail the wire will fail..

so it has to be : 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 = 0.6

please advise.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 319
Joined: Wed Feb 04, 2009 10:32 amFollowed by: 9 members
Location: Delhi
Thanked: 84 times

by sureshbala » Thu Mar 19, 2009 7:42 am
hijazim wrote:Shouldn't it be (0.06)x10 because it is OR not AND probability. As if any of the lightbulbs failed the whole string will fail, so if the 1st or 2nd or ... 10th fail the wire will fail..

so it has to be : 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 + 0.06 = 0.6

please advise.
Folk in addition to this the light will fail if 1st AND 2nd fail and the other don't fail. 1st, 2nd AND 3rd fail and the rest don't....so on...

So instead of considering all this we calculate the probability that none of the light fails for which the probability is (0.94)^10.

Hence the probability that at least one of them fails = 1- (0.94)^10
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1