SOLUTION: A father's age is four times that of his son. After 5 years, it will be three times that of his son. How many more years will take if father's age is to be twice that of his son?

Question 923817: A father's age is four times that of his son. After 5 years, it will be three times that of his son. How many more years will take if father's age is to be twice that of his son?
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
x = the father's age today,
y = the son's age today.

the father's age is equal to 4 times the son's age today.

x = 4y (first equation)

the father's age will be equal to 3 times the son's age in 5 years.

x+5 = 3*(y+5) (second equation)

since x = 4y, then replace x with 4y in the second equation to get:

4y + 5 = 3 * (y + 5)

simplify to get:

4y + 5 = 3y + 15

solve for y to get y = 10

the son's age is 10 today and will be 15 in 5 years.

the father's age is 40 today and will be 45 in 5 years.

45/15 = 3

the father's age will be 3 times the son's age in 5 years.

what you now know.

x = 40
y = 10
x+5 = 45
y + 5 = 15

in how many more years will the father's age be equal to 2 times the son's age?

z = the number of years until the father's age is equal to 2 times the son's age.

the point where we start is when the father is 45 and the son is 15.

45 + z = 2 * (15 + z)

simplify to get:

45 + z = 30 + 2z

solve for z to get z = 15.

in another 15 years, the age of the father will be 2 times the age of the son.

45 + 15 = 60

15 + 15 = 30

60/30 = 2

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