Probability

"Probability" represents the chances of something that will happen. In M'sia education system, we learn probability during secondary school in the maths / statistic (I dun rilly rmb =P). Today I come across with some tricky probability questions:

In a game show, u r given choices of 3 doors. There is only a door with a car behind it whereby the rest has nothing. Lets say if u choose door #1. The host of the show will then open a door that has nothing behind it (eg. #3). After that u r given a chance to switch ur choice between door #1 and #2. What is the probability of getting the car between 2 choices : switch or no switch? Assume that the host will always open one of the empty door...

The correct answer is 2/3 if u change ur selection to door #2 and 1/3 if u remain ur initial choice. Do u agree with this answer? Try figure out the reason behind it ... =P.. At first I thought it should be 1/2 chance for both cases... however if u try to analyze the possible of combination behind it .. u will eventually agree with this answer....

This solution was made by Marilyn vos Savant. She is listed in the Guinness Book of World Records 1986 -1989 for having the highest IQ. Juz google search if you wish to know more detail… =P

The second question should be very common for those who studied "probability" before. I think this question was actually included in the examples in the math textbook. Well, let’s see how much u can recall ur memory….. It is the popular Boy or Girl problem:

We have family A and B, each of the family has 2 children. Given that the elder child is a boy for family A and one of the children is a boy for family B. What is the probability that the other child is a girl for family A and B?

The answer is 1/2 for A and 2/3 for B. Shouldn’t be a tough problem….. (^_^)

Comments

David Chan said…
At this point of writing, I fully agree with the answers to Q2. However, I am still cracking my head at Q1. :-P
David Chan said…
Yes... I accepted the answer for Q1, with full agreement. :-)

The trick is... the host knows what he is doing because he MUST know where the exact answer lies.
Gnu said…
wakao, this becomes a very stressful blog...everytime need to strain my brain whenever I visit...hahaha:p
JacQueLine said…
Aisheh...
How come I can't get the solutions for all the question??
Blur on the explanation somemore..
*_*

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