SOLUTION: A girl is twice as old as her brother and half as old as her father. In 50 years, her brother will be half as old as his father. How old is the daughter now?
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Question 575473: A girl is twice as old as her brother and half as old as her father. In 50 years, her brother will be half as old as his father. How old is the daughter now? Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! let g = daughter's present age
let b = brother's present age
let f = father's present age
;
Write an equation for each statement:
:
"A girl is twice as old as her brother
g = 2b
" and half as old as her father."
g = .5f
:
"In 50 years, her brother will be half as old as his father."
b + 50 = .5(f+50)
b + 50 = .5f + 25
b = .5f + 25 - 50
b = .5f - 25
We can replace .5f with g
b = g - 25
we can replace g with 2b
b = 2b - 25
25 = 2b - b
b = 25 is brothers age
then
2(25) = 50 yrs is the daughter's present age
;
:
Check this using the third equation: that makes the father 100 yrs old
in 50 years: 25 + 50 = .5(100+50); checks out anyway
