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.

Binomial probability

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 882
Joined: Fri Feb 20, 2009 2:57 pmFollowed by: 1 member
Thanked: 15 times
GMAT Score:690
by crackgmat007 » Fri May 08, 2009 8:57 am
If a certain coin is flipped, the probability that the coin will land heads is 1/2. If the coin is flipped 5 times, what is the probability that it will land heads up on the first 3 flips and not on the
last 2 flips?
A. 3/5
B. 1/2
C. 1/5
D. 1/8
E. 1/32

I computed the probability of first 3 flips by using the below formula

5C3 * (1/2)^3 * (1/2)^2 =>This gives me probability of 3 flips being heads.

How to I go from here? Let me know. Tx.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 158
Joined: Tue Sep 30, 2008 8:47 amFollowed by: 1 member
Thanked: 23 times
GMAT Score:660

by DeepakR » Fri May 08, 2009 9:18 am
We know that P=Desired outcome/Total number of outcome

Here Total outcome = 2^5=32
Desired outcome = HHHTT = 1

Hence P = 1/32 = E.)

- Deepak
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 1035
Joined: Wed Aug 27, 2008 10:56 pmFollowed by: 1 member
Thanked: 104 times

Re: Binomial probability

by scoobydooby » Fri May 08, 2009 9:24 am
crackgmat007 wrote:If a certain coin is flipped, the probability that the coin will land heads is 1/2. If the coin is flipped 5 times, what is the probability that it will land heads up on the first 3 flips and not on the
last 2 flips?
A. 3/5
B. 1/2
C. 1/5
D. 1/8
E. 1/32

I computed the probability of first 3 flips by using the below formula

5C3 * (1/2)^3 * (1/2)^2 =>This gives me probability of 3 flips being heads.

How to I go from here? Let me know. Tx.

what you have done answers the question: what is the probability of getting exactly 3 heads in 5 flips?

but here, it is given that we want the first 3 flips to be heads and the other two to be tails=> there is only one way to get first 3 flips as heads,

so we do not need the combination 5C3
so it simply becomes 1*(prob of 3 heads)*(prob of 2 tails)
=>(1/2)^3*(1/2)2
=>(1/2)^5=1/32
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 229
Joined: Tue Jan 13, 2009 6:56 am
Thanked: 8 times
GMAT Score:700

by Uri » Fri May 08, 2009 12:27 pm
the probability of getting head in the 1st toss=1/2
the probability of getting head in the 2nd toss=1/2
the probability of getting head in the 3rd toss=1/2
the probability of getting tail in the 4th toass=1/2
the probability of getting tail in the 5th toass=1/2
So, probability of getting heads in the first three tosses and tails in the last two tosses
=(1/2)^5=1/32
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1