SOLUTION: A girl's present age is the age her brother will be when she will be twice the age he was when her age was half the sum of their present ages. How old are they presently?
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Question 885787: A girl's present age is the age her brother will be when she will be twice the age he was when her age was half the sum of their present ages. How old are they presently?
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Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = the girl's present age
Let = her brother's present age
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Starting at the end:
" when her age was half the sum of their present ages "
Her age was
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" the age he was ( when her age was half the sum of their present ages ) "
Assume the brother is older
The difference in their ages will always be
So, " the age he was " is:
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Proceeding backwards:
" when she will be twice the age he was "
So she will be:
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" the age her brother will be ( when she will be twice the age he was ) "
Add the difference in their ages to get the brother's age
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Proceed to the beginning:
" A girl's present age is ( the age her brother will be ) "
This tells me that
So, the brother is not older
To be called a girl, she must be
8, 12, or 16, which makes her brother
6, 9, or 12
( In order to have whole numbers )
That seems to be the best I can do
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