Probability Problems are one of the topics that we have been solving, since 8th class. However, when it comes to solving these question while aptitude test, then they can be tricky and waste your huge time in solving them. If you know tricks to solve them, then you would need less time to get the answer.
Sometimes the question seems to be complicated but the answer is itself hidden in the question, you just need to read the question carefully. Most of the time, probability questions are based on your thinking and getting the no. of outcomes rather just applying the in depth formulas.
Example: A bag contains 2 red, 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue?
Solution:
Total no. of outcomes can be given as 7C2 i.e. 21.
Now, eliminating blue balls we have 5 balls left, hence no. of possible outcomes can be 5C2 i.e. 10.
Hence, P (E) = 10/21
Example: What is the probability of getting a sum 9 from two throws of a dice?
Solution:
Total no. of outcomes can be given as 36.
Now, we know that to get sum 9, combinations should be like {(3, 6), (4, 5), (5, 4), (6, 3)}.
Therefore, P(E) = 4/36 i.e. 1/9
Example: A coin is thrown 3 times .what is the probability that atleast one head is obtained?
Solution:
Total no. of outcomes can be given as 8.
Sample Space = {HHH, HHT, HTH, THH, TTH, THT, HTT, TTT}
There are only 1 case having no head.
Hence, no. of possible outcomes can be 7.
Therefore, P(E) = 7/8
Example: Two cards are drawn from the pack of 52 cards. Find the probability that both are diamonds or both are kings.
Solution:
Total no. of outcomes can be given as 52C2
There are 2 cases:
If both are diamonds, i.e. 13C2
If both are kings, i.e. 4C2
Since in the question or is given, hence we will add both the cases.
If and is given, we multiply both the cases.
Hence, P(E) =( 13C2 + 4C2 ) / 52C2
This article is contributed by Shushank Mittal.
This post was last modified on July 4, 2022