Question

In a bag there are $21$ balls marked by number$1,2,3,....21$. Two balls are drawn one by one with replacement. What is the probability that from drawn balls first shows odd number and second shows even number.

• A. $\frac{55}{441}$
• B. $\frac{110}{441}$
• C. $\frac{10}{441}$
• D. $\frac{121}{441}$

Answer 1

The correct option is B $\frac{110}{441}$

Total number of balls $=21$

Number of balls marked even $(2,4,6,..,20)=10$

Number of balls marked odd $(1,3,5,7,...21)=11$

Thus required Probability $=$ Probability of first odd $\times$ probability of second even
$=\frac{11}{21}\times \frac{10}{21}$

Required Probablity$=\frac{110}{441}$