Question 619688: A father is three times as old as his son.5 years ago father's age was four times his son's age then.Find their present ages.
Answer by math-vortex(648)   (Show Source):
You can put this solution on YOUR website! Hi, there--
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Let the variable f be the present age of the father.
Let the variable s be the present age of the son.
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Now we use the given information to write equations that model the situation in the problem.
In algebra, a "father is three times as old as his son," can be written as
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The phrase, "5 years ago father's age was four times his son's age then," can be written as
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We have two equations in two variables, so we solve the system to find the values of f and s.
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Substitute 3s for f in the second equation. Simplify.
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Subtract 4s from both sides of the equation. Simplify.
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Add 5 to both sides.
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We see that the son's age is 15. Since the father is three times the age of the son, he is 3*15=45 years old.
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We can check use substituting our answers into the second parameter. Five years ago, was the father four times older than the son? Five years ago the father was 40 and the son was 10. Yes, 40 is four times ten.
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Hope this helps! Feel free to email if you have questions about this,
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Ms.Figgy
math.in.the.vortex@gmal.com
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