Practical Brain teasers for parents (& kids)
-
ChiefKiasu:
Why did I choose A? hmmmm. All have equal chance of being picked and not being picked. So it's really down to luck. If I was the parent, I will just stick with the one I picked bah.
Keke... why did you choose A?SAHM_TAN:
Very stress testing common sense becos I value common sense over IQ LOL.
Hmmmmm I choose A bah
Plus all schools good schools, :evil: go to next phase while putting the name on waitlist for this preferred one. Heehee
I didn't choose C becos going with A and B will have different outcomes so cannot say doesn't matter
-
ChiefKiasu:
Alamak! The the Principal already removed one that does NOT contain his son's name, mean the other one in the box contains his son's name lo. It will be not wise to open the remaining ballot in the box one.Speaking of which, can parents solve this completely hypothetical problem?
3 parents want to get into a school with only 2 remaining vacancies. The names of their children are written down and placed in a ballot box.
One of the parents insisted on being the first to draw. The Principal decided to make it more interesting. The parent will get to draw, but if the ballot he opens is his son's name, then his son will be eliminated and the other 2 parents will get the places in the school.
However, before the parent opens the ballot, the Principal will remove one of the remaining 2 ballots in the box that does NOT contain his son's name. The parent will then get to decide to open either the original ballot he removed, or choose to open the last remaining ballot in the box instead.
What should the parent do?
A) Choose to open his original ballot
B) Choose to open the remaining ballot in the box?
C) It makes no difference whether we choose A or B.
:evil: -
ChiefKiasu:
When the principal takes out one remaining ballot, he can either:Speaking of which, can parents solve this completely hypothetical problem?
3 parents want to get into a school with only 2 remaining vacancies. The names of their children are written down and placed in a ballot box.
One of the parents insisted on being the first to draw. The Principal decided to make it more interesting. The parent will get to draw, but if the ballot he opens is his son's name, then his son will be eliminated and the other 2 parents will get the places in the school.
However, before the parent opens the ballot, the Principal will remove one of the remaining 2 ballots in the box that does NOT contain his son's name. The parent will then get to decide to open either the original ballot he removed, or choose to open the last remaining ballot in the box instead.
What should the parent do?
A) Choose to open his original ballot
B) Choose to open the remaining ballot in the box?
C) It makes no difference whether we choose A or B.
:evil:
1) Put it back because it is the son's name
2) Remove it because it is not the son's name
If action is (1), definitely it is better that parent choose (A) open his original ballot. If action is (2), it points to (C) makes no difference whether choose A or B as the parent would not know for certain the ballot at hand or in the box contains his son's name. So, all options evaluated, the parent should choose (A). -
SAHM_TAN:
...I didn't choose C becos going with A and B will have different outcomes so cannot say doesn't matter
Why does A and B have different outcomes, ie. probabilities? -
arowana:
Alamak! The the Principal already removed one that does NOT contain his son's name, mean the other one in the box contains his son's name lo. It will be not wise to open the remaining ballot in the box one.
Not necessarily. The one in the box may contain another kid's name, and not his son's. This could happen if the parent is currently holding the ballot containing his son's name. -
Pen88n:
The Principal does nothing but just to remove a ballot from the 2 remaining ballots in the box. Assume he has x-ray vision and he knows exactly which ballot to remove. So after the Principal has done his job, one of the ballots that does not contain the parent's son's name will be removed from the problem.When the principal takes out one remaining ballot, he can either:
1) Put it back because it is the son's name
2) Remove it because it is not the son's name
If action is (1), definitely it is better that parent choose (A) open his original ballot. If action is (2), it points to (C) makes no difference whether choose A or B as the parent would not know for certain the ballot at hand or in the box contains his son's name. So, all options evaluated, the parent should choose (A). -
B
Always choose the other option. (switch with the host)
Edit:
If picking his child’s name is the desirable outcome, switch.
If picking his child’s name is NOT the desirable outcome, don’t switch.
The chance of picking his child’s name is higher if he switch. -
wonderm:
Why is the chance of chosing B 1/2?I will choose A because 1/3 the chance it is my child's name, if I chose B, the chance is 1/2.
Correct or not?
Not sure if I hope to get the answer right, that means no common sense leh :nailbite: -
Option
1. Principal remove a paper that is not his son’s name.
2. So left with 2 paper - one with his son name and one with another child’s name.
3. The fact is no matter how he choose between these 2 papers…his son won’t get in. If his paper is his sons name…his son won’t get in…if the paper is the other child’s name, the other child will get it…his son won’t get it…
So it doesn’t matter what he choose… -
Answer is C.
Because it's the 3 parents that want to get into the school? And, not their children?
(I know my answer sound weird. :rotflmao: )
Hello! It looks like you're interested in this conversation, but you don't have an account yet.
Getting fed up of having to scroll through the same posts each visit? When you register for an account, you'll always come back to exactly where you were before, and choose to be notified of new replies (either via email, or push notification). You'll also be able to save bookmarks and upvote posts to show your appreciation to other community members.
With your input, this post could be even better 💗
Register Login