Aptitude | Probability | Question 7
A bag contains 21 balls numbered 1 to 21. two balls are drawn one after another without replacement. Find the probability that both balls are even numbered.
Total numbers in sample space is 21
Probability of choosing any two of them is 21C2.
There are total 10 even numbers from 1 to 21 and probability of choosing any two of them is 10C2
Therefore the required answer is 10C2/21C2 = 3/14