• NEW! FREE Beat The GMAT Quizzes
    NEW! FREE Beat The GMAT Quizzes
    NEW! FREE Beat The GMAT Quizzes
    Hundreds of Questions Highly Detailed Reporting Expert Explanations TAKE A FREE GMAT QUIZ
  • 7 CATs FREE!
    If you earn 100 Forum Points

    Engage in the Beat The GMAT forums to earn
    100 points for $49 worth of Veritas practice GMATs FREE

    Veritas Prep
    VERITAS PRACTICE GMAT EXAMS
    Earn 10 Points Per Post
    Earn 10 Points Per Thanks
    Earn 10 Points Per Upvote
    REDEEM NOW

What is the probability that the sum of two dice will yield

This topic has 2 expert replies and 1 member reply

What is the probability that the sum of two dice will yield

Post

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

Difficult



Manhattan Prep

What is the probability that the sum of two dice will yield a 7, and then when both are thrown again, their sum will again yield a 7? assume that each die has 6 sides with faces numbered 1 to 6.

A. \(1/144\)
B. \(1/36\)
C. \(1/12\)
D. \(1/6\)
E. \(1/3\)

OA B

  • +1 Upvote Post
  • Quote
  • Flag
Post
Total number of ways in which 2 dice can be thrown = 6 * 6 = 36
The combination that will yield a sum of 7 are;
$$1+6$$
$$2+5$$
$$3+4$$
$$4+3$$
$$5+2$$
$$6+1$$
All the 6 different combinations probability of rolling a 7 is 6/36 or 1/6.
To find the probability of this happening twice in a row =>
$$\frac{1}{6}\cdot\frac{1}{6}=\frac{1}{36}\ \ \ \ \ \ Answer=option\ B$$

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Post
If you roll one die, you can always make a sum of 7 if you get the perfect roll on the second die. There's a 1/6 chance you roll the perfect number, so that's the probability of getting a sum of 7. The probability we do that twice in a row is (1/6)(1/6) = 1/36.

You could get down to A or B instantly by noticing that the answer needs to be the square of some very simple fraction of integers.

_________________
If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

  • +1 Upvote Post
  • Quote
  • Flag
Post
AAPL wrote:
Manhattan Prep

What is the probability that the sum of two dice will yield a 7, and then when both are thrown again, their sum will again yield a 7? assume that each die has 6 sides with faces numbered 1 to 6.

A. \(1/144\)
B. \(1/36\)
C. \(1/12\)
D. \(1/6\)
E. \(1/3\)

OA B
Since there are a total of 36 outcomes, and 6 of them yield a sum of 7 (notice that these 6 outcomes are: {1, 6}, {2, 5}, {3, 4}, {4, 3}, {5, 2} and {6, 1}), the probability that the two numbers on the dice yield a sum of 7 is 6/36 = 1/6. The probability that their sum will again yield a 7 is 1/6. Therefore, the probability that the two dice will yield a sum of 7 twice is 1/6 x 1/6 = 1/36.

Answer: B

_________________

Scott Woodbury-Stewart
Founder and CEO
scott@targettestprep.com



See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

  • +1 Upvote Post
  • Quote
  • Flag
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • The Princeton Review
    FREE GMAT Exam
    Know how you'd score today for $0

    Available with Beat the GMAT members only code

    MORE DETAILS
    The Princeton Review

Top First Responders*

1 Ian Stewart 41 first replies
2 Brent@GMATPrepNow 40 first replies
3 Scott@TargetTestPrep 39 first replies
4 Jay@ManhattanReview 32 first replies
5 GMATGuruNY 26 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

Most Active Experts

1 image description Scott@TargetTestPrep

Target Test Prep

159 posts
2 image description Max@Math Revolution

Math Revolution

92 posts
3 image description Brent@GMATPrepNow

GMAT Prep Now Teacher

60 posts
4 image description Ian Stewart

GMATiX Teacher

50 posts
5 image description GMATGuruNY

The Princeton Review Teacher

37 posts
See More Top Beat The GMAT Experts