Tom's father is 3 times old as Tom.  4 years ago he was 4 times older.  How old is TomI cannot figure how to set this up and get answer

Expert Answers
pohnpei397 eNotes educator| Certified Educator

Let T be Tom's age and F be his father's age.

Right now F = 3T because father is three times as old as Tom.

Four years ago, their ages were F-4 and T-4.  So:

4 (T-4) = F-4

If you do the math there, you get

4T - 16 = F -4

So now you substitute in the value of F that we set up earlier.  And you get

4T - 16 = 3T - 4

So now it's pretty simple.

4T = 16 + 3T - 4

T = 12

So Tom is 12.  His father is 36.

Four years ago, he was 8 and Dad was 32.

Tom's father is 3 times old as Tom.  4 years ago he was 4 times older.

sof= toms father and t= tom

f=T3

4 years ago so subtract 4 from both T and F

f-4=T-4

but 4 years ago, toms father was 4 times older then tom so multiply toms side by 4 giving you

f-4=(T-4)*4

f-4=4T-16

but you know that f=3T so substitute that for f

3T-4=4T-16

then subtract 3T from both sides 

-4=T-16

add 16 to both sides

12=T

so tom is 12.

Wiggin42 | Student

Tom's father is 3 times old as Tom.  4 years ago he was 4 times older.  How old is Tom

Let f stand in for Tom's father 

Let t stand in for Tom

f =3t 

 f- 4 = 4( t - 4 )

Now that the equations are set up, you can solve for t. 

mettabear | Student

As mentioned before T is tom's present age....F is his father's.

So at present 3T=F

Four years ago their ages were T-4 and F-4 because his father was four times his age. Therefore

4(T-4)=F-4

Substituting our earlier equivalent of T for F the equation becomes 4(T-4)=3T-4 which becomes

4T-16=3T-4  adding for to both sides makes it

4T-12=3T  subtracting T from both sides you get

T=12   so Tom is currently 12