Probability Ques 32
Question-
A bag contains 20 balls (5 green balls and certain number of red balls and blue balls). If 2 balls are taken out one after another without replacement, the probability that the first ball is red and the second ball is green is $\frac{2}{19}$. What is the difference between the number of red and blue balls in the bag?
(1) 2
(2) None of these
(3) 1
(4) 4
(5) 3
(Canara Bank PO Exam, 23.12.2018)
Show Answer
Correct Answer: (3)
Solution: (3)
Red and blue balls $=15$
If number of red balls be $x$, number of blue balls $=15-x$
$\therefore$ Required probability $=\frac{x_{C_{1}}}{20_{C_{1}}} \times \frac{5_{C_{1}}}{19_{C_{1}}}$ $=\frac{5 x}{20 \times 19}=\frac{x}{76}$
$\therefore \frac{x}{76}=\frac{2}{19}$
$\Rightarrow x=\frac{2 \times 76}{19}=8$
$\therefore$ Blue balls $=15-8=7$
$\therefore$ Required difference $=8-7=1$
BETA
