SOLUTION: Robert is 1/2 as old as his father. Twelve years ago he was 1/3 as old as his father was then. Find their present ages

Question 105932: Robert is 1/2 as old as his father. Twelve years ago he was 1/3 as old as his father was then. Find their present ages
Answer by Earlsdon(6294) (Show Source): You can put this solution on YOUR website!
Start by letting R = Robert's present age and F = Father's present age.
From the problem you can write:
1) "Robert (R) is half as old as his father (F)"
2) "Twelve years ago, he was 1/3 as old as his father was then"
So now you have a system of equations with two unknowns (R and F) and you can use any of the accepted methods for solving these for R and F.
You can simplify these equations by clearing the fractions.
1) Multiply through by 2.
1a)
2) Multiply through by 3.
2a) Now substitute the F from the simplified equation 1a) into the simplified equation 2a).
Simplify and solve for R by subtracting 2R from both sides.
Add 36 to both sides.
This is Robert's present age.

This is the father's present age.
Check:

OK, and...

OK
RELATED QUESTIONS
Robert is one-half as old as his father. Twelve years ago, Robert was one-third as old as (answered by stanbon)

Robert is one half as old as his father. Twelve years ago, Robert was one third as old as (answered by stanbon)

robert is one half as old as his father. twele years ago, robert was one-third as old as... (answered by drcole)

A father is twice as old as his son. Twelve years ago the father was four times as old as (answered by lwsshak3)

I need help!!! A father is twice as old as his son. Twelve years ago the father was... (answered by mananth)

1. when gary and rowena were married, rowena was two years younger than gary. how old was (answered by Paul)

A father is 30 years older than his son, one year ago he was 4 times as old as his son,... (answered by mananth)

A father is now 3 times older than his son.12 years ago he was 6 times as old as his... (answered by josmiceli)

1. (Age) a father is now three times as old as his son. Twelve years ago he was six times (answered by Edwin McCravy)