SOLUTION: if today a father is four times as old as his son and five years ago he was five times as old as his son, find their present age

Algebra ->  Customizable Word Problem Solvers  -> Age -> SOLUTION: if today a father is four times as old as his son and five years ago he was five times as old as his son, find their present age       Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 720620: if today a father is four times as old as his son and five years ago he was five times as old as his son, find their present age
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +f+ = Father's age now
Let +s+ = Son's age now
given:
(1) +f+=+4s+
(2) +f+-+5+=+5%2A%28+s+-+5+%29+
----------------------
(2) +f+-+5+=+5s+-+25+
(2) +5s+-+f+=+20+
By substitution:
(2) +5s+-+4s+=+20+
+s+=+20+
and
(1) +f+=+4s+
(1) +f+=+4%2A20+
(1) +f+=+80+
The Father is 80
The Son is 20
--------------
check:
5 years ago, the Father was +75+
5 years ago, the Son was +15+
+75+=+5%2A15+
+75+=+75+
OK