Math Olympiad question for Sec 3 and 4 : Find Cheryl's Birthday

Anoop Kumar

Anoop Kumar

@anoop-kumar-GDGRCn • Oct 26, 2024
You might have came across this question on internet. Sharing here for possible explanation.

maths-question_650x400_41428997958
Actual Question paper:
SASMO-q24
I have the answer for the question. I will g<a href="https://mothership.sg/2015/04/p5-logic-question-is-actually-a-math-olympiad-question-for-sec-3-and-4-students/" target="_blank" rel="nofollow noopener noreferrer">"P5" logic question is actually a Math Olympiad question for Sec 3 and 4 students - Mothership.SG - News from Singapore, Asia and around the world</a>ve the answer later.
Question is not the answer. Question is explanation ☕

Are you good enough logician to explain the question and your answer? 😘
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  • Anoop Kumar

    Anoop Kumar

    @anoop-kumar-GDGRCn • Apr 15, 2015

    Ok, No taker here.
    Here is the official explanation. I have given the link at letter "i" in word give.
    <a href="https://mothership.sg/2015/04/p5-logic-question-is-actually-a-math-olympiad-question-for-sec-3-and-4-students/" target="_blank" rel="nofollow noopener noreferrer">"P5" logic question is actually a Math Olympiad question for Sec 3 and 4 students - Mothership.SG - News from Singapore, Asia and around the world</a>

    SASMO-Question-solution Question 1 - How they ruled out may 15?
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  • Kaustubh Katdare

    Kaustubh Katdare

    @thebigk • Apr 16, 2015

    I tried for a while but then realised that solving such problems ain't my cup of tea. So I decided to have a cup of tea and get back to work 😔 .
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  • Ankita Katdare

    Ankita Katdare

    @abrakadabra • Apr 16, 2015

    I somehow zeroed down to 16th as the answer, but wasn't sure if that's correct.
    Had this come as a multiple choice answer question in an exam, I would've answered 16 and moved on.
    #-Link-Snipped-# May 15 is still bugging me.
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  • Anoop Kumar

    Anoop Kumar

    @anoop-kumar-GDGRCn • Apr 16, 2015

    Something can't be explained simply isn't worth explaining 😁.
    Any explanation you have to rule out all other 9 dates.
    Here is another <a href="https://mothership.sg/2015/04/p5-logic-question-is-actually-a-math-olympiad-question-for-sec-3-and-4-students/?fb_comment_id=838139176272653_838247516261819#f285138074" target="_blank" rel="nofollow noopener noreferrer">"P5" logic question is actually a Math Olympiad question for Sec 3 and 4 students - Mothership.SG - News from Singapore, Asia and around the world</a> Seems promising but I will not spend my precious mind explaining more. 😛
    Quoted from comment:

    "The answer is August 17. The answer key is flawed. A lot of you have misread the question. They are not mind readers and Albert is not given any more information than Bernard. There are only two rules : Albert knows the month and Bernard knows the date. They can only tell each other whether they know the date now or not.

    “Albert : I don’t know but I know that Bernard doesn’t know too"
    If Bernard was told the date and immediately knew, it would be either May 19 or June 18. They both will realise this instantly and eliminate those two date: So we are left with:

    May : 15 or 16
    June : 17
    July : 14 or 16
    August : 14, 15, 17

    “Bernard : At first I didn’t know, but now I do”
    If Albert knew the month and the month was June, he would have known its June 17, but it isn’t June. So Bernard knows that it isn’t June. So he narrows it down to:
    May: 15 or 16
    July : 14 or 16
    August : 14, 15, 17

    But Bernard knows the day. So if he knows the date now, it must be August 17.

    “Albert: Then I also know.”
    Albert realises this too because Bernard can only be 100% sure it was on August 17 if he was given 17 as the day. If Bernard was given either 14, 15 or 16, he still wouldn’t know which month."
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