SOLUTION: Stevie is twice as old as his brother. Four years ago he was four times as old as his brother. Find their present ages. Can anyone help me, I'm having a lot of trouble coming up w

Algebra ->  Customizable Word Problem Solvers  -> Age -> SOLUTION: Stevie is twice as old as his brother. Four years ago he was four times as old as his brother. Find their present ages. Can anyone help me, I'm having a lot of trouble coming up w      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 189681: Stevie is twice as old as his brother. Four years ago he was four times as old as his brother. Find their present ages. Can anyone help me, I'm having a lot of trouble coming up with an equation. I can't thank you guys enough!!

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Let s=Stevie's age and b=Brother's age

So this means that
s-4 = Stevie's age 4 years ago, and
b-4=Brother's age 4 years ago


"Stevie is twice as old as his brother" translates to s=2b


"Four years ago he was four times as old as his brother" translates to s-4=4%28b-4%29


s-4=4%28b-4%29 Start with the second equation.


2b-4=4%28b-4%29 Plug in s=2b


2b-4=4b-16 Distribute.


2b=4b-16%2B4 Add 4 to both sides.


2b-4b=-16%2B4 Subtract 4b from both sides.


-2b=-16%2B4 Combine like terms on the left side.


-2b=-12 Combine like terms on the right side.


b=%28-12%29%2F%28-2%29 Divide both sides by -2 to isolate b.


b=6 Reduce.


So Stevie's brother is currently 6 years old. Also, he was 2 years old 4 years ago.


s=2b Go back to the first equation


s=2%286%29 Plug in b=6


s=12 Multiply


So Stevie is currently 12 years old. Four years ago, he was 8 years old. Notice how 8=2%2A4 (ie 8 yrs old is 4 times greater than 2 yrs old)