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# 35 - Probability

Author Message
Joined: 31 Dec 1969

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Location: Russian Federation
GMAT 3: 740 Q40 V50
GMAT 4: 700 Q48 V38
GMAT 5: 710 Q45 V41
GMAT 6: 680 Q47 V36
GMAT 9: 740 Q49 V42
GMAT 11: 500 Q47 V33
GMAT 14: 760 Q49 V44
WE: Supply Chain Management (Energy and Utilities)

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11 Nov 2004, 03:34
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

a question from the GMATCLUB forsaleqeustions:

what is the prob of bearing two boys from four born babies ?

a. 1/5
b. 1/8
c. 1/2
d. 3/8
e. 6/11

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Senior Manager
Joined: 16 Aug 2004
Posts: 320

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Location: India

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11 Nov 2004, 03:59
Sweet and Simple Option c

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GMAT Club Legend
Joined: 15 Dec 2003
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11 Nov 2004, 04:31
D) 3/8
Prob of getting boy: 1/2
Prob of getting girl: 1/2
Prob of getting exactly 2 boys and 2 girls: (1/2)^4
Pattern: BBGG --> 2 boys can take 4C2=6 different positions
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Best Regards,

Paul

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11 Nov 2004, 12:58
yeah paul, u are correct

conceiving 2 boys from 4 babies can be possible in 4C2 = 6 ways
and probability to get boy baby / gal baby is (1/2)

So the probability to get exactly 2 boy babies - 6 * (1/2)^4 = 3/8
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Perseverance, Hard Work and self confidence

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Joined: 28 Jul 2004
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17 Nov 2004, 07:02
total outcomes 1/2^4=16

possible combinations

B1 G G B2
B2 G G B1
B1 G B2 G
B2 G B1 G
G B1 B2 G
G B2 B1 G

so ...... 6/16=3/8
_________________

Jim

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

Joined: 31 Dec 1969

Kudos [?]: [0], given:

Location: Russian Federation
GMAT 3: 740 Q40 V50
GMAT 4: 700 Q48 V38
GMAT 5: 710 Q45 V41
GMAT 6: 680 Q47 V36
GMAT 9: 740 Q49 V42
GMAT 11: 500 Q47 V33
GMAT 14: 760 Q49 V44
WE: Supply Chain Management (Energy and Utilities)

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17 Nov 2004, 10:04
using binominal formula will give a straightforward answer: ( 1/2+1/2)^4 gives all posible outcomes.

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17 Nov 2004, 10:04
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