M4maths Previous Puzzles

17 Nov 2015 Probability

A bag contain 8 red and 5 white balls. 2 balls are drawn at random. What is the probability that both are white

OPtion

1) 5/16
2) 1/26
3) 2/13
4) 1/5
5) 3/26
6) 1/16
7) 5/39
8) 1/39
9) 1/13
10)None of these

Solution

Let S be the sample space and E be the event of drawing 2 white balls.
Then, n(S) = Number of ways of drawing 2 balls out of 13
= 13 C 2 = 13*12/2 = 78
n(E) Number of ways of drawing 2 balls out of 5
5 C 2 = 5*4/2 = 10
Therefore
P(E) = n(E)/n(S) = 10/78 = 5/39
Option 7)

Correct Option: 7 Best Solution (23)

MURUGESAN.P   9 years AGO

probability for taking 2 white ball =5C2=10
total probability =13C2=78
therefore,
10/78=5/39

Like? Yes (5) | No (1)  

premlata   9 years AGO

There are 13C2 ways to select 2 balls from 13 balls.
And , There are 5C2 ways to select 2 white balls out of 5 white balls.

Probability of all 2 white balls begin drawn:
5C2 / 13C2 = 5/39

Like? Yes (3) | No   

RAHUL KUMAR   9 years AGO

P(E) = n(E)/n(s) = (8c0*5c2)/13c2 = 5/39
option (7) is correct.

Like? Yes (2) | No   

pooja   9 years AGO

n(E)/n(S)
n(E)=5C2*8C0
n(S)=13C2
therefore, 5/39

Like? Yes (2) | No   

Shobhit sengar   9 years AGO

Total balls are = 13
White balls are = 5
Ways to draw 2 balls from bag = 13c2
Ways to draw 2 balls from 5 white balls = 5c2
So prob of drawing two white balls from bag = 5c2/13c2
= 5/39

Like? Yes (2) | No (1)  

Shanawaz Mohammed   9 years AGO

5c2/13c2

Like? Yes (1) | No   

MRITUNJAY   9 years AGO

p=5c2/13c2
=5/39

option 7

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ramakrishnateja   9 years AGO

out of 13 balls 2 balls which are white is to be taken.
so,prob of both to be white is 5c2/13c2 = 5/39
so

Like? Yes (1) | No   

JEGATHA.H   9 years AGO

8+5=13
let S be the sample space n(S)= 13c2 = 78
event of getting white ball n(E)= 5C2=10
P(E)=n(E)/n(S)=10/78=5/39

Like? Yes (1) | No   

Akshaya   9 years AGO

Totally we have 13 balls( 8 red + 5 white)
Two balls are drawn at random,
Probability that both balls are white = 5C2/13C2 = 5/39

Like? Yes (1) | No   

aditya vasudeva   9 years AGO

Total No. of possibilies for picking two balls = 13c2 ...
As total no. of balls 8+5 = 13
Der should be two white balls only there for possible no of white balls 5c2 becoz total no. of white balls = 5 and we need two white balls ..
P(2 white balls) = 5c2/13c2
Answer = 5/39

Like? Yes (1) | No   

ramji   9 years AGO

P(E)=n(E)/n(s)
5*4/13*12
5/39

Like? Yes (1) | No   

krishna veni   9 years AGO

no.of balls are 13c2...the chance of getting two white balls is 5c2..
so probability is 5c2/13c2=10/78=5/39

Like? Yes (1) | No   

Praveen Bora   9 years AGO

n(S)=13C2
n(E)=5C2
P(E)=n(E)/n(S)
=5C2/13C2
=5/39

Like? Yes (1) | No   

Pooja Shaw   9 years AGO

let S=sample space
n(S)=no of ways of drawing 2 balls out of (8+5)=13C2=(13*12)/(2*1)=78
let E=event o f getting both white balls
n(E)=no of ways of drawing 2 balls out of 5=5C2=(5*4)/(2*1)=10
P(E)=n(E)/n(S)=10/78=5/39
Thus,correct option is 7)5/39

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keerthi choudhry   9 years AGO

total number of balls=8+5=13
no of ways for drawing 2balls out of 13=(13 *12)/2
THEREFORE THE NUMBER OF WAYS FOR DRAWING 2 balls that is white =(5*4)/2
thus answer=((5*4)/2)/((13*12)/2)
=5/39
option:7

Like? Yes (1) | No   

Jaikumar Bhatia   9 years AGO

n(S)=13C2=78
n(E)=5C2=10

Therefore
P(E)=n(E)/n(S)
=10/78
=5/39

Ans is 5/39
Option is (7)

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kanika dhapola   9 years AGO

total outcome= 13c2
both are white balls= 5c2
probablity=5c2/13c2
=5/39 ans

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sahil arora   9 years AGO

no. of ways of selecting 2 balls out of 13 balls are
13C2= 13*12/2= 78

no.of ways of selecting 2 balls out of 5 balls are
5C2=5*4/2=10

hence probability that both the balls selected are white is =10/78=5/39

Like? Yes (1) | No   

rajkumar   9 years AGO

prob = (fav events)/(tota events)

total events = 13C2
fav events = 5C2

prob = 5/39

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Surabhi Yadav   9 years AGO

Favourable outcome=5C2
Total outcome=13C2
=5/39

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Irfan   9 years AGO

n(s)=78
Probability of getting both are white = 5c2/78
P(e)=5/39

Like? Yes (1) | No   

Yadu Vir Singh   9 years AGO

Total balls are = 13
White balls are = 5
Ways to draw 2 balls from bag = 13c2
Ways to draw 2 balls from 5 white balls = 5c2
So prob of drawing two white balls from bag = 5c2/13c2
= 5/39

Like? Yes (2) | No (2)