Question 1096769: Richard is 5 times older than his son. 5 years ago, he is 15 times the age of his son, What is Richard's age today? Answer by ikleyn(52800) (Show Source):
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Richard is 5 times as old as his son is. 5 years ago, he was 15 times the age of his son. What is Richard's age today?
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R = 5*S (1) ("now")
R-5 = 15*(S-5) (2) (5 years ago)
In (2), replace R by 5*S, based on (1). You will get
5*S - 5 = 15*(s-5) ====>
5S - 5 = 15S - 75 ====> 75-5 = 15S - 5S ====> 10S = 70 ====> S = = 7.
Answer. The son is 7 years now. Richard is 5*7 = 35 years old.
