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# a certain bag contains 6 marbles of which 4 are red and 2

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Manager
Joined: 13 Aug 2018
Posts: 52
a certain bag contains 6 marbles of which 4 are red and 2  [#permalink]

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23 Nov 2019, 12:13
00:00

Difficulty:

25% (medium)

Question Stats:

72% (01:22) correct 28% (01:40) wrong based on 39 sessions

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a certain bag contains 6 marbles of which 4 are red and 2 are white in color. if babu is to pick out two marbles from the bag simultaneously & at random, what is the probability that one is red & other one is white?
a. 1/5
b. 1/3
c. 1/15
d. 8/15
e. 4/9

Posted from my mobile device
Math Expert
Joined: 02 Aug 2009
Posts: 8284
a certain bag contains 6 marbles of which 4 are red and 2  [#permalink]

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24 Nov 2019, 04:08
jackfr2 wrote:
a certain bag contains 6 marbles of which 4 are red and 2 are white in color. if babu is to pick out two marbles from the bag simultaneously & at random, what is the probability that one is red & other one is white?
a. 1/5
b. 1/3
c. 1/15
d. 8/15
e. 4/9

Posted from my mobile device

Total ways to pick 2 marbles——-6C2=15
Ways to pick one of each ———-4C1*2C1=4*2=8

Probability =8/15

D
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Re: a certain bag contains 6 marbles of which 4 are red and 2  [#permalink]

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24 Nov 2019, 04:11
1
jackfr2 wrote:
a certain bag contains 6 marbles of which 4 are red and 2 are white in color. if babu is to pick out two marbles from the bag simultaneously & at random, what is the probability that one is red & other one is white?
a. 1/5
b. 1/3
c. 1/15
d. 8/15
e. 4/9

Posted from my mobile device

Red & blue = 2c1 * 4/6 * 2/5 = 8/15
IMO D
Manager
Joined: 04 Apr 2015
Posts: 249
GMAT 1: 650 Q49 V31
GPA: 3.59
Re: a certain bag contains 6 marbles of which 4 are red and 2  [#permalink]

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24 Nov 2019, 04:33
Probability of 1R and 1B = p(r)xP(b) +P(b)xP(r) as he can pick any ball first

case1 : red ball first and blue ball second = P(r)xP(b)=(2red/total 6) * 4 blue/5 total .....................1 ball has already been picked
case2 : blue ball first and red ball second =P(b)xP(r)= 4blue/total 6)* 2 red/5 total..........................1 ball has already been picked

required prob (case1 or case 2)= P(r)xP(b) +P(b)xP(r)= 4/15+ 4/15= 8/15.......(D)
Re: a certain bag contains 6 marbles of which 4 are red and 2   [#permalink] 24 Nov 2019, 04:33
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