Quantitative Aptitude Ques 236
Question: A bag contains 13 white and 7 black balls. Two balls are drawn at random. What is the probability that they are of the same colour? [IBPS (PO) 2012]
Options:
A) $ \frac{41}{190} $
B) $ \frac{21}{190} $
C) $ \frac{59}{190} $
D) $ \frac{99}{190} $
E) $ \frac{77}{190} $
Show Answer
Answer:
Correct Answer: D
Solution:
- The number of balls in bag $ =13+7=20 $
$ \therefore $ $ n,(S)={}^{20}C _2=190 $ For same colour of ball, $ n,(E _1)={}^{13}C _2=78 $ and $ n,(E _2)={}^{7}C _2=21 $ Hence, required probability, $ P(E)=\frac{n,(E _1)}{n,(S)}+\frac{n,(E _2)}{n,(S)}=\frac{78}{190}+\frac{21}{190}=\frac{99}{190} $
BETA
