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 →

Probablilty of snow on Saturday

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 641
Joined: Tue Feb 14, 2012 3:52 pmFollowed by: 8 members
Thanked: 11 times
by gmattesttaker2 » Thu May 29, 2014 7:58 am
Hello,

Can you please tell me how to solve for Statement 2:

If the probability of snow is the same every day this week, what is the probability of snow on Saturday?

1.The probability of snow on Monday is 1/7.
2.The probability having of no snow on both Thursday and Friday is 36/49.

OA: D

1) Since prob. of snow is the same every day this week => P(snow on Sat.) = 1/7 - [spoiler]Suff./spoiler]

2) P(No snow on Thu. and No snow on Fri.) = 36/49
=> P( Snow on Thu. and Snow on Fri. ) = 13/49

However, I was not able to solve from here.

Thanks for your help.

Regards,
Sri
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

by Brent@GMATPrepNow » Thu May 29, 2014 8:13 am
gmattesttaker2 wrote: If the probability of snow is the same every day this week, what is the probability of snow on Saturday?

1) The probability of snow on Monday is 1/7.
2) The probability having of no snow on both Thursday and Friday is 36/49.
Target question: What is the probability of snow on Saturday?

Given: The probability of snow is the same every day this week

Statement 1: The probability of snow on Monday is 1/7.
If the probability of snow is THE SAME every day this week, then the probability of snow on Saturday is also 1/7
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: The probability having of no snow on both Thursday and Friday is 36/49.
Let p = probability of snow on Saturday.
Since the probability of snow is the same every day this week, we know that p = probability of snow on Thursday and p = probability of snow on Friday.
Also, (1-p) = probability of NO SNOW on Thursday and (1-p) = probability of NO SNOW on Friday.

Statement 2 says: P(no snow on Thursday AND no snow on Friday) = 36/49
Rewrite as: P(no snow on Thursday) x P(no snow on Friday) = 36/49
Rewrite as: (1-p) x (1-p) = 36/49
Simplify: (1-p)² = 36/49
Solve: (1-p) = 6/7
So, p = 1/7
In other words, the probability of snow on Saturday is 1/7
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer = D

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members
Location: New York, NY
Thanked: 13060 times
GMAT Score:790

by GMATGuruNY » Thu May 29, 2014 8:31 am
gmattesttaker2 wrote:Hello,

Can you please tell me how to solve for Statement 2:

If the probability of snow is the same every day this week, what is the probability of snow on Saturday?

1.The probability of snow on Monday is 1/7.
2.The probability having of no snow on both Thursday and Friday is 36/49.
Statement 1:
Since the probability of snow is the same for every day of the week, P(snow on Saturday) = 1/7.

Statement 2:
Test whether the value given in statement 1 -- P(snow) = 1/7 -- is the ONLY value that will satisfy statement 2.
If P(snow) = 1/7, then P(no snow) = 6/7.
Implication:
P(no snow on Thursday AND no snow on Friday) = 6/7 * 6/7 = 36/49.
This works.
NO OTHER FRACTION multiplied by itself will yield the required probability of 36/49.
Thus, like statement 1, statement 2 indicates that P(snow) = 1/7.
SUFFICIENT.

The correct answer is D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

by Brent@GMATPrepNow » Thu May 29, 2014 9:44 am
gmattesttaker2 wrote:Hello,

Can you please tell me how to solve for Statement 2:

If the probability of snow is the same every day this week, what is the probability of snow on Saturday?

1.The probability of snow on Monday is 1/7.
2.The probability having of no snow on both Thursday and Friday is 36/49.

OA: D

1) Since prob. of snow is the same every day this week => P(snow on Sat.) = 1/7 - [spoiler]Suff./spoiler]

2) P(No snow on Thu. and No snow on Fri.) = 36/49
=> P( Snow on Thu. and Snow on Fri. ) = 13/49

However, I was not able to solve from here.

Thanks for your help.

Regards,
Sri
Hi Sri,

I've highlighted (in green) a small problem with your solution.
P(No snow on Thu. and No snow on Fri) = 36/49, this means that the probability of no snow on BOTH days is 36/49
If we want to apply the complement here, we can say that the probability of NOT HAVING no snow on BOTH days is 13/49. NOTE: This includes the possibility that there's no snow on ONE of the days and snow on the other day.
This conclusion is different from the conclusion that you drew. You concluded that 13/49 is the probability of having snow on both days. This is not true.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1