Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

A. 1/133225 - I thought this was the correct answer, because from what I understand if we want to find out the prob that BOTH siblings will have the same birthday is much higher than just 1/365. Even though they are independent events, which is 1/365 per time a child is born, in order for both of your child to have the same bday the odds presumably increases. Can someone please correct my logic. Thanks.

Re: What is the probability that two siblings, ages 6 and 8 ... [#permalink]

Show Tags

02 May 2012, 14:44

1

This post received KUDOS

The first sibling is born on a given day, that probably is 1/1. The probability of the second having a birthday on the same day is 1/365.

You have to think as the two as independent events. The probably of one person having a birthday on ANY date is 1/1, not 1/365. The second has to match.

Re: What is the probability that two siblings, ages 6 and 8 [#permalink]

Show Tags

01 Apr 2015, 05:10

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Re: What is the probability that two siblings, ages 6 and 8 [#permalink]

Show Tags

02 Apr 2015, 12:50

Expert's post

Hi All,

The explanation offered by pstrench is the most straight-forward way of dealing with this question. The approach taken by iNumbv isn't 'wrong' so much as it's 'incomplete.'

You CAN calculate the probability that two people are BOTH born on any individual day.

eg. What is the probability that they are BOTH born on January 1st?

(1/365)(1/365)

Since we have to account for the FULL YEAR though, we would need to consider all 365 options. You don't really need to write them all out though, since you know that each is the same product. This gives us...

(365)(1/365)(1/365)

The first two parentheses 'cancel out', leaving us with....

Re: What is the probability that two siblings, ages 6 and 8 [#permalink]

Show Tags

04 Apr 2015, 10:17

EMPOWERgmatRichC wrote:

Hi All,

The explanation offered by pstrench is the most straight-forward way of dealing with this question. The approach taken by iNumbv isn't 'wrong' so much as it's 'incomplete.'

You CAN calculate the probability that two people are BOTH born on any individual day.

eg. What is the probability that they are BOTH born on January 1st?

(1/365)(1/365)

Since we have to account for the FULL YEAR though, we would need to consider all 365 options. You don't really need to write them all out though, since you know that each is the same product. This gives us...

(365)(1/365)(1/365)

The first two parentheses 'cancel out', leaving us with....

I am able to follow your solution till you consider both of them to be born on 1st Jan. So each has probability of having bday on 1st jan is = 1/365 Then why we should not multiply these two probabilities ?? as 1/365 * 1/365 I'm a bit confused here ... Aditya _________________

Re: What is the probability that two siblings, ages 6 and 8 [#permalink]

Show Tags

04 Apr 2015, 12:26

1

This post received KUDOS

Expert's post

adityadon wrote:

EMPOWERgmatRichC wrote:

Hi All,

You CAN calculate the probability that two people are BOTH born on any individual day.

eg. What is the probability that they are BOTH born on January 1st?

(1/365)(1/365)

GMAT assassins aren't born, they're made, Rich

Hi Rich ,

I am able to follow your solution till you consider both of them to be born on 1st Jan. So each has probability of having bday on 1st jan is = 1/365 Then why we should not multiply these two probabilities ?? as 1/365 * 1/365 I'm a bit confused here ... Aditya

Hi Adiya,

If you take another look at my explanation, you'll see that I DID multiply (1/365)(1/365)....This is the probability that 2 people are born on January 1st.

Since there are 365 days in a normal year and since the question asks for the probability of two people being born on the SAME day (any day, not just on January 1st), we have to think about ALL 365 days.

So there are 365 individual calculations that equal (1/365)(1/365).

MBA Admission Calculator Officially Launched After 2 years of effort and over 1,000 hours of work, I have finally launched my MBA Admission Calculator . The calculator uses the...

Final decisions are in: Berkeley: Denied with interview Tepper: Waitlisted with interview Rotman: Admitted with scholarship (withdrawn) Random French School: Admitted to MSc in Management with scholarship (...

The London Business School Admits Weekend officially kicked off on Saturday morning with registrations and breakfast. We received a carry bag, name tags, schedules and an MBA2018 tee at...