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14.Probability
easy
Two balls are drawn at random with replacement from a box containing $10$ black and $8$ red balls. Find the probability that First ball is black and second is red.
A
$\frac{20}{81}$
B
$\frac{20}{81}$
C
$\frac{20}{81}$
D
$\frac{20}{81}$
Solution
Total number of balls $=18$
Number of red balls $=8$
Number of black balls $=10$
Probability of getting first ball black $=\frac{10}{18}=\frac{5}{9}$
The ball is replaced after the first draw.
Probability of getting second ball as red $=\frac{8}{18}=\frac{4}{9}$
Therefore, probability of getting first ball as black and second ball as red $=\frac{5}{9} \times \frac{4}{9}=\frac{20}{81}$
Standard 11
Mathematics
