SOLUTION: A father is 60 years old and his son is half his age. How old was the boy when his father was four times his age?

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Question 420706: A father is 60 years old and his son is half his age. How old was the boy when his father was four times his age?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A father is 60 years old and his son is half his age.
How old was the boy when his father was four times his age?
:
let y = years ago when dad's age was 4 times son's age
:
60 - y = 4(30 - y)
60 - y = 120 - 4y
-y + 4y = 120 - 60
3y = 60
y = 60%2F3
y = 20 years ago
:
Then 30 - 20 = 10 yrs old, boy's age when his dad was 40 yrs old