math problem.jpg
Math problem
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Claude
- cheese lizard
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- Joined: 16 Jan 2010, 00:14
- Location: Sydney Australia
Math problem
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Cheers, Claude.
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HansV
- Administrator
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- Joined: 16 Jan 2010, 00:14
- Status: Microsoft MVP
- Location: Wageningen, The Netherlands
Re: Math problem
Spoiler
July 16
Explanation:
1) A doesn't know, and A knows that B doesn't know either.
The 19th occurs in May only, and the 18th in June only, so if C tells A that her birthday is in May or June, A cannot know that B doesn't know. Hence May and June aren't possible.
2) B now knows the birthday.
The 14th occurs in both remaining months July and August, so if C tells B that her birthday is on the 14th, B still doesn't know which month. Therefore the 14th isn't possible.
3) A now knows too.
If C had told A that the month is August, he would still be in the dark: it could be the 15th or 17th. So August isn't possible either. The only remaining possibility is July 16.
Explanation:
1) A doesn't know, and A knows that B doesn't know either.
The 19th occurs in May only, and the 18th in June only, so if C tells A that her birthday is in May or June, A cannot know that B doesn't know. Hence May and June aren't possible.
2) B now knows the birthday.
The 14th occurs in both remaining months July and August, so if C tells B that her birthday is on the 14th, B still doesn't know which month. Therefore the 14th isn't possible.
3) A now knows too.
If C had told A that the month is August, he would still be in the dark: it could be the 15th or 17th. So August isn't possible either. The only remaining possibility is July 16.
Best wishes,
Hans
Hans
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Claude
- cheese lizard
- Posts: 6241
- Joined: 16 Jan 2010, 00:14
- Location: Sydney Australia
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Rudi
- gamma jay
- Posts: 25455
- Joined: 17 Mar 2010, 17:33
- Location: Cape Town
Re: Math problem
The Simple Solution:
If Cheryl was my friend I'd simply tell her not to expect a Birthday present from me unless she tells me explicitly!
If Cheryl was my friend I'd simply tell her not to expect a Birthday present from me unless she tells me explicitly!
Regards,
Rudi
If your absence does not affect them, your presence didn't matter.
Rudi
If your absence does not affect them, your presence didn't matter.
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HansV
- Administrator
- Posts: 78444
- Joined: 16 Jan 2010, 00:14
- Status: Microsoft MVP
- Location: Wageningen, The Netherlands
Re: Math problem
More about this puzzle: Cheryl's Birthday: Singapore's maths puzzle baffles world.
One comment:
One comment:
"After spending so much time together, thinking of Cheryl's birthdate, Albert and Bernard soon fell in love with each other and forgot all about Cheryl"
Best wishes,
Hans
Hans
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Rudi
- gamma jay
- Posts: 25455
- Joined: 17 Mar 2010, 17:33
- Location: Cape Town
Re: Math problem
HansV wrote:More about this puzzle: Cheryl's Birthday: Singapore's maths puzzle baffles world.
One comment:
"After spending so much time together, thinking of Cheryl's birthdate, Albert and Bernard soon fell in love with each other and forgot all about Cheryl"
Regards,
Rudi
If your absence does not affect them, your presence didn't matter.
Rudi
If your absence does not affect them, your presence didn't matter.