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mathematics for South Africa

When is Cheryl’s birthday? Second hint

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This is the second part of the solution for the problem which I provided a couple of days ago. If you have not read this then please start from the first part of this problem – When is Cheryl’s birthday.

Yesterday I provided the first hint to you, and we concluded with the following:

STATEMENT 2: Albert: I don’t know when Cheryl’s birthday is, but I know that Bernard does not know too.

The question to ask is: how does Albert KNOW that Bernard does NOT KNOW the birthday!

We can also ask this another way – HOW could Bernard KNOW the birthday, and how would Albert also KNOW that Bernard KNOWS?
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When is Cheryl’s birthday? First hint

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Yesterday I posed a When is Cheryl’s birthday, which is to find Cheryl’s birthday given just a few basic facts. If you have not read the When is Cheryl’s birthday, please do this first.

Contrary to what I said yesterday about this problem, whereas it create a viral storm on the Internet, it was actually a problem from the Singapore and Asian Mathematics Olympiad for senior secondary students. You can read more about it Mothership if you are interested.

Today we will look at this problem and work towards a solution.
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Problem #1: When is Cheryl’s birthday? The problem which became viral

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Here is a mathematical problem which did the rounds on Twitter and other social media a couple of weeks ago. Everyone thought it was too difficult for learners to understand, and this was presented at the Grade 8 level in Singapore (one of the world’s best countries for mathematical learner proficiency, where South Africa is in last place).

The question is simple “When is Cheryl’s birthday”.
See if you can work this out for yourself, and I can assure you that there IS enough information given.

Over the next few days I will provide hints until we arrive at the answer.

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