Math mystery (3)

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Math mystery (3)

Postby Ruud » Sun Apr 30, 2006 11:26 pm

2 mathematicians meet each other in the street and start a conversation.

"How many children do you have?"

"3"

"How old are they?"

"You'll have to guess. The product of their ages is 36"

"Hmm.. too many options. What else can you tell me?"

"OK. The sum of their ages is equal to the number of the house at the other side of the street."

"I'm close, but still missing a clue"

"Right. The eldest kid plays piano"

"That's it! Thanks!"


Do you know the age of the mathematician's kids?

Ruud.
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Re: Math mystery (3)

Postby Cec » Mon May 01, 2006 4:24 am

Ruud wrote:Do you know the age of the mathematician's kids?

It seems too easy so I suspect I'm wrong - I'll say 3, 6 and 2years.
I'm still wading through all the replies in MM(2) which has given me a lot to think about - enjoying all these posts but wish I was quicker on the uptake. I'd be able to 'compete' better if a joke was allowed to wind up each thread or would it spoil things?

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Postby udosuk » Mon May 01, 2006 7:50 am

The kids are 2,2,9 respectively...

There're only 8 combinations of the ages triples:

Code: Select all
Ages   Sum
1,1,36  38
1,2,18  21
1,3,12  16
1,4,9   14
1,6,6   13
2,2,9   13
2,3,6   11
3,3,4   10


Now only (1,6,6) & (2,2,9) totalling to the same sum, 13, which must be the street number of that house across the street...

There is an eldest kid, so apprently they cannot be a pair of 6-year-old twins... (But in fact almost every twins have an elder one... anyway that's how the story's supposed to go...)
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Postby emm » Mon May 01, 2006 11:08 am

Why does the number of the house have to be 13?
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dis-ambiguation

Postby Pat » Mon May 01, 2006 11:28 am

emm wrote:Why does the number of the house have to be 13?


because the number of the house
was not sufficient to answer the question -
an extra clue was still needed for dis-ambiguation:
"The sum of their ages is equal to the number of the house at the other side of the street."

"I'm close, but still missing a clue"
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Maths Mystery (3)

Postby Cec » Mon May 01, 2006 12:36 pm

emm wrote:Why does the number of the house have to be 13?

I note Pat has answered this but I still have the same query as emm.

The three clues don't say the house across the street has to be No. 13 - it could be any number say No. 14 in which case the ages of the three kids could also be the 1,4,and 9 years combination. Taking this further, as the house number is not disclosed the kid's ages could therefor be any one of the eight age combinations listed by udosuk. Am I missing something which restricts the answer solely to 2,2 and 9 years?

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Postby Ruud » Mon May 01, 2006 1:55 pm

Hi Cec,

if you look at the list of all possible combinations, you will notice that all combinations sum up to a different total, except the combinations 1,6,6 and 2,2,9, which both sum up to 13.

If the house number would not have been 13, the second mathematician would have known the answer and not need another clue.

Ruud.
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Mystery maths (3)

Postby Cec » Mon May 01, 2006 2:37 pm

Yes Ruud I get it now. A very clever riddle.

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Postby MCC » Mon May 01, 2006 2:41 pm

I believe there is an assumption being made here, and that is that both mathematicians can see the number of the house across the road.

If they cannot see the number then there is no answer.

So both mathematicians can see the number, any number other than 13 and the riddle can be solved, only if the number is 13 does it require an additional clue.


MCC

I see cec has finally got it. I will leave my post anyway.
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