father son age problem

[ifthyder]

A father's age was three times that of his son five years ago,While five years hence the father will be twice as old as his son. Determine their present ages ?

A 13years , 10 years
B 40 years 16years
C 35 years 15 years
D 45 years 18 years

[cramya]

It should be C) 35 and 15

[vivek.kapoor83]

fastest way is takinng option and calculate.
lilke from d ..if u subtract -- 5 , that will give their age..3 times...true and if u add five,father will be of 40 and son 20, So both codn satisfy.No need to calculate.

[stop@800]

fastest way is takinng option and calculate.
lilke from d ..if u subtract -- 5 , that will give their age..3 times...true and if u add five,father will be of 40 and son 20, So both codn satisfy.No need to calculate.

Good one

[raunekk]

imo:c

[canuckclint]

I am not getting this one

two equations I set up

f-5 = 3(s-5)
f=2s

How do you get the answer algebraically?

[cramya]

Let x be fathers present age and y be the sons present age

A father's age was three times that of his son five years ago:

x-5 = 3(y-5)
x-3y = -10 (1)

While five years hence the father will be twice as old as his son:

x+5 = 2(y+5)
x-2y = 5 (2)


Subtract 1 and 2:

x-3y = -10
x-2y = 5

-3y-(-2y) = -10 - 5

-y = -15

y =15

x=35

Hope this helps!