It is currently 20 Oct 2017, 11:13

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

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

Another interesting one from the Hakob's set: What is the

Author Message
SVP
Joined: 03 Feb 2003
Posts: 1603

Kudos [?]: 303 [0], given: 0

Another interesting one from the Hakob's set: What is the [#permalink]

Show Tags

19 Mar 2003, 10:14
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Another interesting one from the Hakob's set:

What is the probability of bearing two boys from four born babies?

A) 1/5
B) 1/8
C) 1/2
D) 3/8
E) 6/11

Kudos [?]: 303 [0], given: 0

Intern
Joined: 18 Mar 2003
Posts: 4

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

Location: Munich

Show Tags

19 Mar 2003, 10:31
isn't it necessary to know how many girls and boys there are in the group of four babies

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

Founder
Joined: 04 Dec 2002
Posts: 15587

Kudos [?]: 28511 [0], given: 5114

Location: United States (WA)
GMAT 1: 750 Q49 V42

Show Tags

19 Mar 2003, 11:07
commander wrote:
isn't it necessary to know how many girls and boys there are in the group of four babies

not really, you just start out assuming that you can have only boys and girls; not neutrals

Then I think you will need to calculate how many ways you can get 2 boys out of a group of 4, which is C(2,4) = 6

Then probability kicks in....

I am not good in these, but I will try, I got 3/8

Kudos [?]: 28511 [0], given: 5114

Intern
Joined: 18 Mar 2003
Posts: 4

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

Location: Munich

Show Tags

19 Mar 2003, 11:22
pleas explain? :help

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

Intern
Joined: 18 Mar 2003
Posts: 4

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

Location: Munich

Show Tags

19 Mar 2003, 11:26
okay I got it: It's a combined problem:

chance of someone being a girl or boy is 1/2.

taking 2 out of four can be done in like you said in: 2C4=6 ways

so the probability is: 6x1/2x1/2x1/2x1/2= 3/8

Now how can one remember this rule?

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

Founder
Joined: 04 Dec 2002
Posts: 15587

Kudos [?]: 28511 [0], given: 5114

Location: United States (WA)
GMAT 1: 750 Q49 V42

Show Tags

19 Mar 2003, 11:32
commander wrote:
pleas explain? :help

Probability is not my strong point, but I think I got this one or at least I can explain the logic behind it:
whatever your probability will be to have 2 out of 4, it needs to be multiplied by 6 since you have 6 ways to pick them.

So, the answer basically depends on the probability.

I got the result by 1/2*1/2*1/2*1/2

I assumed you get 1/2 probability to have a boy/girl at any point in time.
So, I got 1/2 for boy, 1/2 for another boy, 1/2 for girl, and 1/2 for girl, (you need to get exactly 2 boys and 2 girls). So, it is 1/16

6*1/16=3/8

--=-

Kudos [?]: 28511 [0], given: 5114

Founder
Joined: 04 Dec 2002
Posts: 15587

Kudos [?]: 28511 [0], given: 5114

Location: United States (WA)
GMAT 1: 750 Q49 V42

Show Tags

19 Mar 2003, 11:33
commander wrote:
okay I got it: It's a combined problem:

chance of someone being a girl or boy is 1/2.

taking 2 out of four can be done in like you said in: 2C4=6 ways

so the probability is: 6x1/2x1/2x1/2x1/2= 3/8

Now how can one remember this rule?

You were faster than I

Kudos [?]: 28511 [0], given: 5114

Founder
Joined: 04 Dec 2002
Posts: 15587

Kudos [?]: 28511 [0], given: 5114

Location: United States (WA)
GMAT 1: 750 Q49 V42

Show Tags

19 Mar 2003, 23:09
stolyar wrote:

dude

Kudos [?]: 28511 [0], given: 5114

Manager
Joined: 24 Jun 2003
Posts: 54

Kudos [?]: 1 [0], given: 0

Show Tags

10 Sep 2003, 14:11
Isn't there a formula for this type of problem:

nCk * p^k * (1-p)^(n-k)

it works out to 3/8 also

Htown

Kudos [?]: 1 [0], given: 0

10 Sep 2003, 14:11
Display posts from previous: Sort by