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

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

What is the difference

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 809
Joined: Wed Mar 24, 2010 10:10 pmFollowed by: 4 members
Thanked: 50 times
by akhpad » Mon Aug 23, 2010 12:42 pm
What is the difference in these two problems [in meaning]?

1. What is the probability of getting at least 2 heads in a row on three flips of a fair coin? = 3/8

2. What is the probability of getting at least 2 heads on three flips of a fair coin? = 1/2
Last edited by akhpad on Mon Aug 23, 2010 12:56 pm, edited 1 time in total.
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: 422
Joined: Mon Aug 09, 2010 11:47 amFollowed by: 1 member
Thanked: 22 times
GMAT Score:680

by beatthegmatinsept » Mon Aug 23, 2010 12:51 pm
What is the difference in these two problems [in meaning]?

1. What is the probability of getting at least 2 heads in a row on three flips of a fair coin?
This one asks about the following possible scenaiors:
Case 1
First flip - Heads
Second flip - Heads
Third Flip - Heads

Case 2
First flip - Heads
Second flip - Heads
Third Flip - Tails

Case 3
First flip - Tails
Second flip - Heads
Third Flip - Heads

2. What is the probability of getting at least 2 heads on three flips of a fair coin?
This one talks about getting 2 or more heads on a total of 3 flips (BUT it does not care about them being in a row or back to back). So a possible scenario that this could have, that the other one isnt asking for would be:

First flip - Heads
Second flip - Tails
Third Flip - Heads

Does that help?
Being defeated is often only a temporary condition. Giving up is what makes it permanent.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 659
Joined: Mon Dec 14, 2009 8:12 amFollowed by: 3 members
Thanked: 32 times

by Gurpinder » Mon Aug 23, 2010 12:52 pm
akhp77 wrote:What is the difference in these two problems [in meaning]?

1. What is the probability of getting at least 2 heads in a row on three flips of a fair coin?

2. What is the probability of getting at least 2 heads on three flips of a fair coin?

1. What is the probability that you will get 2 heads together on 3 flips.
---> so HHT or HHT --> you cannot have HTH because the 2 heads are not together.

2. Here you still want 2 heads, but they dont have to occur together.
----> so you can have HHT, HTH, THH.

I hope that clarifies!
"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 422
Joined: Mon Aug 09, 2010 11:47 amFollowed by: 1 member
Thanked: 22 times
GMAT Score:680

by beatthegmatinsept » Mon Aug 23, 2010 12:53 pm
Gurpinder wrote:
akhp77 wrote:What is the difference in these two problems [in meaning]?

1. What is the probability of getting at least 2 heads in a row on three flips of a fair coin?

2. What is the probability of getting at least 2 heads on three flips of a fair coin?

1. What is the probability that you will get 2 heads together on 3 flips.
---> so HHT or HHT --> you cannot have HTH because the 2 heads are not together.

2. Here you still want 2 heads, but they dont have to occur together.
----> so you can have HHT, HTH, THH.

I hope that clarifies!
@ Gurpinder - 1 says 'at least'.. You missed the HHH scenaio I think.. Or I understood this wrong. :)
Being defeated is often only a temporary condition. Giving up is what makes it permanent.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 659
Joined: Mon Dec 14, 2009 8:12 amFollowed by: 3 members
Thanked: 32 times

by Gurpinder » Mon Aug 23, 2010 2:06 pm
beatthegmatinsept wrote:
Gurpinder wrote:
akhp77 wrote:What is the difference in these two problems [in meaning]?

1. What is the probability of getting at least 2 heads in a row on three flips of a fair coin?

2. What is the probability of getting at least 2 heads on three flips of a fair coin?

1. What is the probability that you will get 2 heads together on 3 flips.
---> so HHT or HHT --> you cannot have HTH because the 2 heads are not together.

2. Here you still want 2 heads, but they dont have to occur together.
----> so you can have HHT, HTH, THH.

I hope that clarifies!
@ Gurpinder - 1 says 'at least'.. You missed the HHH scenaio I think.. Or I understood this wrong. :)
Yes, you are right!!!! But I wasn't trying to list all possibilities; rather just give examples because akhp77 said he wanted help with the meaning.

:D
"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 809
Joined: Wed Mar 24, 2010 10:10 pmFollowed by: 4 members
Thanked: 50 times

by akhpad » Mon Aug 23, 2010 8:43 pm
Finally, I understood this way

1. What is the probability of getting at least 2 heads in a row on three flips of a fair coin?

Whatever comes [H>=2] in consecutive three flips.

HHT, THH, HHH,


2. What is the probability of getting at least 2 heads on three flips of a fair coin?

Here includes all possibilities.
HHH, HHT, HTH, THH

Am I right.
Last edited by akhpad on Mon Aug 23, 2010 9:43 pm, edited 1 time in total.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Senior | Next Rank: 100 Posts
Posts: 74
Joined: Fri Jun 25, 2010 6:33 pm
Thanked: 3 times

by vijaynaik » Mon Aug 23, 2010 9:26 pm
No. In Q1. in a row is crucial. So the Heads have to be consecutive.

HHT, THH, HHH --- in these at least 2 heads are in a row.

Q2. Heads doesn't have to be consecutive but should have at least 2 Heads.

HTH -- in this 2 heads are separated by a Tail. and other possibilities THH,HHT,HHH.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 659
Joined: Mon Dec 14, 2009 8:12 amFollowed by: 3 members
Thanked: 32 times

by Gurpinder » Tue Aug 24, 2010 8:05 am
akhp77 wrote:Finally, I understood this way

1. What is the probability of getting at least 2 heads in a row on three flips of a fair coin?

Whatever comes [H>=2] in consecutive three flips.

HHT, THH, HHH,


2. What is the probability of getting at least 2 heads on three flips of a fair coin?

Here includes all possibilities.
HHH, HHT, HTH, THH

Am I right.
Your almost getting there buddy!!

1. What is the probability of getting at least 2 heads in a row on three flips of a fair coin?

The key to this problem are the words "in a row".

All this means is that the 2 heads HAVE TOO come up TOGETHER. You can't have HTH -- because the 2 heads are seperated by the T. Therefore, you can have HHT or THH < - in either case the 2 heads are together.

2. What is the probability of getting at least 2 heads on three flips of a fair coin?

For this you, the heads DO NOT need to come up TOGETHER. So all you need would be 2 heads but can be in any position. HHT, HTH, THH, HHH.

So you are absolutely right on this one.

I hope that helps!
"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1