Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 03 May 2015, 03:14

### GMAT Club Daily Prep

#### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# A couple has 3 children. Find the probability that atleast

 Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
Manager
Joined: 15 Jul 2005
Posts: 106
Followers: 1

Kudos [?]: 4 [0], given: 0

A couple has 3 children. Find the probability that atleast [#permalink]  06 Oct 2005, 21:06
1
This post was
BOOKMARKED
A couple has 3 children. Find the probability that atleast one is a boy. Assume likelyhood of having a boy or a girl is equal and independent.

a) 1/8
b) 1/3
c) 2/7
d) 7/8
e) 5/8

Last edited by chets on 06 Oct 2005, 21:17, edited 1 time in total.
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5078
Location: Singapore
Followers: 22

Kudos [?]: 184 [0], given: 0

[#permalink]  06 Oct 2005, 21:12
P(Boy) = P(Girl) = 1/2
Events are independent, mutually exclusive.

P(one boy) = P(Boy and Girl and Girl) = 1/2 * 1/2 * 1/2 = 1/8
Manager
Joined: 15 Jul 2005
Posts: 106
Followers: 1

Kudos [?]: 4 [0], given: 0

[#permalink]  06 Oct 2005, 21:17
Sorry, I made a mistake in the question.

It should read, find the probability that atleast 1 is boy.
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5078
Location: Singapore
Followers: 22

Kudos [?]: 184 [0], given: 0

[#permalink]  06 Oct 2005, 21:24
chets wrote:
Sorry, I made a mistake in the question.

It should read, find the probability that atleast 1 is boy.

Then probability = 1 - P(all girls) = 1 - 1/8 = 7/8

Ans: D
SVP
Joined: 05 Apr 2005
Posts: 1733
Followers: 5

Kudos [?]: 38 [0], given: 0

Re: Easy Probability [#permalink]  06 Oct 2005, 21:48
P(0 boy) = (1/2)^3=1/8
so, P(at least a boy)=total prob-P(0 boy)=1-1/8=7/8

alt: p(a boy)=1/2, p(2 boy)=1/4, p(3 boy)=1/8
so, P(at least a boy) = p(a boy)+p(2 boy)+p(3 boy)=1/2+1/4+1/8= 7/8
Senior Manager
Joined: 14 Apr 2005
Posts: 419
Location: India, Chennai
Followers: 1

Kudos [?]: 6 [0], given: 0

Re: Easy Probability [#permalink]  06 Oct 2005, 21:59
chets wrote:
A couple has 3 children. Find the probability that atleast one is a boy. Assume likelyhood of having a boy or a girl is equal and independent.

a) 1/8
b) 1/3
c) 2/7
d) 7/8
e) 5/8

P(Atleast 1 boy) = 1 - P(All being girls)
= 1 - (1/2*1/2*1/2)
= 1 - 1/8
= 7/8
Senior Manager
Joined: 22 Jun 2005
Posts: 364
Location: London
Followers: 1

Kudos [?]: 5 [0], given: 0

[#permalink]  07 Oct 2005, 01:20
It's D

The probability of not having any boy is
1/2*1/2*1/2=1/8

The probability of having at least one boy:

1-1/8 = 7/8.
[#permalink] 07 Oct 2005, 01:20
Similar topics Replies Last post
Similar
Topics:
6 A couple has two children, one of whom is a girl. If the probability 3 05 Sep 2014, 02:58
12 The probability that a family with 6 children has exactly 16 08 Jan 2010, 16:56
Probability--Atleast 5 14 Apr 2007, 06:51
A couple wants to have 4 children. The probability of 5 24 Nov 2005, 04:24
A couple wants four children. If the probability of having a 3 20 Oct 2005, 15:19
Display posts from previous: Sort by

# A couple has 3 children. Find the probability that atleast

 Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group and phpBB SEO Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.