Question

After five years the age of a father will be thrice the age of his son, whereas five years ago , he was seven times as old as his son was. What is father's present age?

Answer 1

let father's present age be x years and son's present age be y years.

five years ago father was x-5 years and son was y-5 years.

accordingly,

x-5= 7(y-5)

x-5= 7y-35

x-7y=-30.........(1)

now,

after five years,

father will be x+5 years and son will be y+5 years

accordingly,

x+5= 3(y+5)

x+5= 3y+15

x-3y=10.............(2)

now subtracting (2) from (1),

x -7y= -30

-

x+3y = -10

-4y= -40

therefore present age of son= y= 10

now, substituting age of son in eq (2)

x-3y= 10

x-30= 10

x= 40

therefore father is presently 40 years old