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        riddles >> hard >> daughter's ages
        
(Message started by: klbarrus on Jul 25^th, 2002, 5:03pm)

Title: daughter's ages
Post by klbarrus on Jul 25^th, 2002, 5:03pm

The product of Dr. D's daughter's ages is 72, or 3*3*2*2*2. Trying out various combinations, we get these possibilities:

18, 2, 2; sum 22
9, 4, 2; sum 15
12, 3, 2; sum 17
6, 6, 2; sum 14
8, 3, 3; sum 14
6, 4, 3; sum 13

Since Dr. S can't figure out the ages from their sum, it must be either 6, 6, 2 or 8, 3, 3 as they both add to 14, and the rest are unique. Dr. D said "his oldest" so this means his daughters are 8, 3, 3.

Of course, Dr. D might have been talking about the oldest twin of the 6 year old pair ;)

Title: Re: daughter's ages
Post by Zy Baxos on Jul 26^th, 2002, 8:53pm

Addition to solution above:

You are ignoring a large number of possible age combo's:

1,1,72 - all right, not *that* possible
1,2,36 - "
1,3,24
1,4,18
1,6,12
1,8,9

Fortunately, all of these combinations have unique sums, so your answer still holds :)

Regards,
Zy

Title: Re: daughter's ages
Post by klbarrus on Jul 27^th, 2002, 11:33pm

Doh! Thanks, I skipped all the factors of 1 as you said.