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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.
There is a bunch of lessons on age word problems
- Age problems and their solutions
- A fresh formulation of a traditional age problem
- Really intricate age word problem
- Selected age word problems from the archive
- Age problems for mental solution
in this site.
Read them and become an expert in solving age problems.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Age word problems".
Save the link to this online textbook together with its description
Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson
to your archive and use it when it is needed.