 Hello, I am welcome to the session. I am Deepika here. Let's discuss the question we see. A bag consists of 10 balls, each marked with one of the digits 0 to 9. If four balls are drawn successively with replacement from the bag, what is the probability that none is marked with the digit 0? Now we know that the trials of a random experiment are called Bernoulli trials. If they are finite in number, they are independent. Each trial has exactly two outcomes, success or failure and the probability of success remains the same in each trial. Again, we know that probability of x successes is equal to ncx into q raise to power n minus x into p raise to power x, where x is from 0 to n and q is equal to 1 minus p. So this is a key idea behind our question. We will take the help of this key idea to solve the above question. So let's start the solution. Let's denote the number of balls marked with digit 0 in the four balls. The drawing of balls is done with replacement. Therefore the trials are Bernoulli trials. Now clearly x has the binomial distribution with n is equal to 4, p is equal to 1 over 10 where p is the probability of drawing a number marked with digit 0. Therefore q is equal to which is given by 1 minus p is equal to 1 minus 1 over 10 and that is again equal to 9 over 10 and the probability that none of the ball is marked with the digit 0. Therefore the probability that none of the ball is marked with digit 0 is given by probability of x is equal to 0. Now according to our key idea we have probability of x successes is equal to ncx into q raise to power n minus x into p raise to power x where x is from 0 to n and q is equal to 1 minus p. Now here we have n is equal to 4, p is equal to 1 over 10 and q is equal to 9 over 10. Therefore probability of x is equal to 0 is equal to 4 c 0 into 9 over 10 raise to power 4 minus 0 into 1 over 10 raise to power 0 and this is again equal to 4 c 0 which is 1 into 9 over 10 raise to power 4 into 1 because 1 over 10 raise to power 0 is 1 so this is again equal to 9 over 10 raise to power 4 and the probability that none of the ball is marked with the digit 0 is 9 over 10 raise to power 4. So this is the answer for the up of question. This completes our session. I hope the solution is clear to you. Bye and have a nice day.