SOLUTION: A father is 4 times older as old as his daughter. In 20 years he will be only twice as old as his daughter. How old are the father and daughter now?

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Question 170817: A father is 4 times older as old as his daughter. In 20 years he will be only twice as old as his daughter. How old are the father and daughter now?
Found 2 solutions by stanbon, Mathtut:
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
A father is 4 times older as old as his daughter. In 20 years he will be only twice as old as his daughter. How old are the father and daughter now?
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NOW DATA:
Let daughter be x yrs. old
father is 4x yrs old
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In 20 years DATA:
daughter will be x+20 yrs old
father will be 4x+20 yrs old
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EQUATION:
father = 2*daughter's age
4x+20 = 2(x+20)
4x+20 = 2x+40
2x = 20
x = 10 (daughter's age NOW)
4x = 40 (father's age NOW)
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Cheers,
Stan H.

Answer by Mathtut(3670) (Show Source):
You can put this solution on YOUR website!
call fathers age f and daughters age d
:
f=4d....eq 1
f+20=2(d+20)..eq 2
:
take f's value from eq 1 and plug it into eq 2 and distribute the right side of eq 2
:
4d+20=2d+40
:
2d=20
:
daughters age
fathers age