Present Age of Each

[nycmath]

A father is 4 times as old as his son. In 20 years the father will be twice as old as his son. Find the present age of each.

[Eigenvalue]

Let f be the age of the father and s be the age of the son

1. Write the equations
f=4s
f+20=2(s+20)
f=2s+40-20=2s+20

2. Set the 2 equations equal by substituting 4s for f
4s=20+2s
20=2s
s=10

3. Substitute 10 for s
f=4(10)=40

The son is 10 years old and the father is 40 years old

[Eigenvalue]

Let f be the age of the father and s be the age of the son

1. Write the equations
f=4s
f+20=2(s+20)
f=2s+40-20=2s+20

2. Set the equations equal by substituting 4s for f
4s=2s+20
2s=20
s=10

3. Substitute 10 for s
f=4(10)
f=40

The son is 10 years old and the father is 40 years old.

[Eigenvalue]

Let f be the age of the father and s be the age of the son

1. Write the equations
f=4s
f+20=2(s+20)
f=2s+40-20=2s+20

2. Set the equations equal by substituting 4s for f
4s=2s+20
2s=20
s=10

3. Substitute 10 for s
f=4(10)
f=40

The son is 10 years old and the father is 40 years old.

[nycmath]

Let f be the age of the father and s be the age of the son

1. Write the equations
f=4s
f+20=2(s+20)
f=2s+40-20=2s+20

2. Set the 2 equations equal by substituting 4s for f
4s=20+2s
20=2s
s=10

3. Substitute 10 for s
f=4(10)=40

The son is 10 years old and the father is 40 years old

Thanks but why post the same reply three times?