Aptitude - Problems on Ages - Discussion

3. 

A father said to his son, "I was as old as you are at the present at the time of your birth". If the father's age is 38 years now, the son's age five years back was:

[A]. 14 years
[B]. 19 years
[C]. 33 years
[D]. 38 years

Answer: Option A

Explanation:

Let the son's present age be x years. Then, (38 - x) = x

2x = 38.

x = 19.

Son's age 5 years back (19 - 5) = 14 years.


88Gguyu said: (Jul 23, 2010)  
What is meaning of "I was as old as you are at the present at the time of your birth".

Shruthi said: (Aug 1, 2010)  
The meaning was "at the time of son's birth, father age was son's present age".

Shan said: (Aug 21, 2010)  
The meaning is [if father age is 30 @ past then son age is 0]
-----
Then [if son age is 30 @ present then father age is 60] that is
--------
The explanation... See that (the past age of father= the present age of son)

Goud said: (Aug 27, 2010)  
The meaning is ' the sons presant age= father's age at the time son's birth

Karthick said: (Aug 31, 2010)  
Meaning of 38 - x = x ?

Sriram said: (Oct 2, 2010)  
@ Karthik

Father's present age - Son's age = Father's age at the time of Son's birth.

Prachi said: (Dec 10, 2010)  
Thanks dear.........

Prasath said: (Jan 27, 2011)  
Meaning of 2x = 38.

Vijaykumar said: (Feb 5, 2011)  
2x=38 ?

Shikha said: (Feb 12, 2011)  
(38-X)=X so X taking other side negative becmes positive X.so 2X
38-X=x
38=2x
x=19

Tridib Adak said: (Feb 22, 2011)  
Really helpful.

Nijin said: (Feb 23, 2011)  
Thank you friends.

Gayu said: (May 30, 2011)  
Thank you my friends.

Stella said: (Jun 15, 2011)  
Friends, I have one doubt.

Father's present age-son's age=father's age at the time of son's birth.

38-x=x.

Here son's age & father's age at the time of son's birth both are assigned to x.

How is it possible? why we can't take two variables?

Vivek Jain said: (Jun 30, 2011)  
38-x=x means that
after substracting x(son's present age) from 38(father's current age),we will get the fathers age at the time of his son's birth and which was also x.

V.Prasanthi said: (Oct 9, 2011)  
Take three reverse number is descending order. Now reverse the result and add the reversed number with the original. You will get 1089 as the answer.

[A] 765 567+198;198+891+1089 [B] 129 921+891;891+198+1089

[C] 225 522+729;729+927+1089 [D] 139 931+991;991+199+1089

Anandraj N said: (Nov 7, 2011)  
Can we assign X to both father and sons age ie., (38 - x) = x ?

Vijay said: (Nov 23, 2011)  
How did 2x come into picture?

Priya said: (Dec 5, 2011)  
(38 - x) = x? How it came? Can't get that.

Vignesh said: (Dec 14, 2011)  
@stella you are right.

Sharanya said: (Jan 6, 2012)  
@priya.

The son is as old as his father was at the time of his (sons) birth. Thus if you subtract the sons present age from the fathers present age you will find the age of the father at the time of the sons birth ie 38-x.

This must be equal to the sons present age.

Hence 38-x=x.

Ramya said: (Jan 20, 2012)  
Thank you.

Mercy said: (Jan 25, 2012)  
Son's age is exactly to half to the fathers age, suppose if fathers age is 38 then sons age is 38/2 i.e, 19 and 5 years back his is 19-5 =14.

Anirudh said: (Jan 30, 2012)  
See, let any variable x be the age of son.

The fathers age is equal to sons present age wen the son was born.

So if you deduct the sons age ie 38-x it shows the faters age when the child was born and eqating to x shows the childs present age so it is a valid result :)

Lavanya said: (Jun 2, 2012)  
@stella.
It was clearly given in the question that "I was as old as, you are at the present, at the time of your birth". Means son present age= father age at the time of son birth. So, for these two we have to assign same variable.

Preshkitha said: (Jun 5, 2012)  
We can't take two variables because present son's age is equal to the age of father when the son was born. Okay. ?

Kusuma said: (Jun 20, 2012)  
How can we tell that the son age is exactly half to his father age and not any other option.

Guru Praveen said: (Jul 15, 2012)  
Hi Friends,

In the question itself it is clearly said Son's Present age is same as Father age at the time of his son's birth.

So sons age will be half the age of father at any time.

So if sons age is x, then father age is 2x.

Given father present age is 38, so obviously son's present age will be half of father's hence sons age is 38/2 which is 19 years.

Sons age before 5 years is 19-5=14.

Nayak said: (Sep 15, 2012)  
Hello Everyone

I like everyone the way u think all guys. Really it help me a lot to analyze the problems.. thanks

Vijay Ananad said: (Aug 17, 2013)  
Fathers current age is 38, since we don't know son's age we will consider his age as X. So now,

Fathers current age is 38--------------------(eqn 1).

Sons current age is X.

When his son was born then his fathers current age should be X(because "I was as old as you are at the present at the time of your birth")(sons present age is X, so when father told this dialogue then at that time his age should also be X).

So at the birth sons age is 0 and his fathers age is X.
During Birth:

Son's current age = 0.
Fathers current age = X.

Now son has grown upto X years so father will also grow up to X years, so Sons age will be 0+X and fathers age will be X+X.

Fathers age =X+X=2X-----------------------(eqn 2),

Equating (1)&(2),

2X = 38.

X = 19.

Sons current age is 19 and 5 years back he will be 19-5 = 14.

K. Jay Prakash Rao said: (Feb 26, 2014)  
Let the son's present age be x years. Then, (38 - x) = x. -> why x is subtracted from 38?

2x = 38. -> how 2x = 38 its not mentioned in the question?

x = 19.

Son's age 5 years back (19 - 5) = 14 years.

Bhagyashri said: (Apr 18, 2014)  
Father's age (38-x).

Son's age x.
Son's age before 5 years (x-5).

Father's age before 5 years (38-x) -5.

(38-x) -5 = (x-5).
33-x = x-5.
33+5 = x+x.
38 = 2x.
x = 19.

Therefore son's age before 5 years (x-5) = (19-5) = 14.

Khushi said: (Apr 25, 2014)  
Father's age now is 38; let son's age be x.
Son's current age = age of his father on his birth.i.e. x.

If we subtract son's current age from father's current age ie x=(38-x).
We get father's age @ the time of son's birth which is x.

And we observe father's age @the time of son's birth = x = son's current age.
38-x = x.

Dhanendr said: (May 31, 2014)  
I still not got exact intelligible meaning of that sentence told by father.

Suraj Dalvi said: (Jun 8, 2014)  
Father current year 38.

Son age consider x.
The sons age = father's.
Age at the time son's birth.

Father's present age - Son's age = Father's age
At the time of Son's birth.

38-x = x.
38 = x+x.
38 = 2x.
x = 38/2 .
x = 19.

Son's age 5 years back (x-5)=(19-5)=14 is correct answer !

Titash.810 said: (Jul 17, 2014)  
How can we say that Both X is same variable?
I mean why 38-X = X,

Why not 38 - X = Y, where Y is Father's age.
At the time of Son's birth.

Rabnawaz said: (Nov 7, 2014)  
Don't write "x" just place the numbers the alphabetical symbols are quit disturbing.

Dattu said: (Nov 16, 2014)  
Please explain confidentially.

Bindu said: (Jan 25, 2015)  
38-x = x? Can any one explain in detail?

Pradeep Kumar Maurya said: (Jan 30, 2015)  
38-x = x.

LHS RHS.

Keep the variable one side and numbers also a side,

We get,

38 = x+x (Because LHS-x when it will put on RHS then sign will be change as per rule).

Now, 38 = 2x.

38/2 = x (Here coefficient of x i.e. 2 will be denominator of 38).

19 = x.

You can say x = 19.

Nanda said: (Feb 7, 2015)  
@ Kusuma:

"I was as old as you are at the present at the time of your birth".

Means:- Let us assume that son has 10 years now then.

At present father age = 10 years before to son + 10 years after to son.

i.e 20 so son age is half of the father age.

Shradha said: (Mar 18, 2015)  
From solution we found that, x = 19 i.e. son's present age.

Father's present age = 38.

Given statement: "I was as old as you are at the present at the time of your birth".

i.e age of father when his was born.

Hence, Father's present age - Son's present age.

= 38-19 = 19. Father's age at the time of his son's birth.

And son's present age + Father's age at the time of his son's birth.

i.e 19+19 = 38. Its prove check it out.

Divya Agrawal said: (Mar 31, 2015)  
Can be taken as at the time of son birth father was x year old,

Both increases with like son = 1, father = x+1.

Son = 2, father = x+2.

Now situation is son is x, means father is 2x.

Akshay said: (May 7, 2015)  
I am still not getting 38-x = x?

Gandharva said: (May 18, 2015)  
38-x = y.

Here 38 is the present age of the father, and x is the present age of the son,

If we subtract 38 from x, we get father's age at the time of son's birth i.e. "y".

According to given condition, father's age at the time of son's birth = Son's present age.

Therefore here y = x means 38-x = x.

Aditya said: (Aug 15, 2015)  
How can this man give birth to a child when he is only 19?

Siri said: (Sep 18, 2015)  
Hai.

Already we initialed that son age is:x.

Then how? We again take x as father age at the time of sons birth.

Praveen said: (Sep 23, 2015)  
Is there any new process to solve guys without taking the help of variables.

Ranjiraj Nair said: (Oct 3, 2015)  
Father Son.

Present age -> 38 let be 'x'.

At Birth -> 38-x (x-x) = 0.

By statement: I was means father was was as old as you as you are at the present i.e. son at the time of son's birth so,

Present age of son = x years.

Fathers age at son's birth = (38-x).

Just equate it: x = 38-x.

x = 19.

They want 5 years ago so 19-5 = 14.

Venkata Ravi said: (Oct 18, 2015)  
Any another way to solve this problem?

Ramya said: (Oct 31, 2015)  
How can you subtract the past age of father from his present age to get get the present age of son? I can't get you.

Kamlesh said: (Nov 28, 2015)  
Reading which part of the question I should go for making this equation 38-x = x.

Shahid said: (Dec 26, 2015)  
38-x age of father at born time.

Krishna said: (Dec 27, 2015)  
Here is the clarity:

Let present age of son = x.

Given father present age = 38.

According to logic when son age is 0 (during birth), fathers age is x.

Then when son's age is x, then father's age is 38.

So x-0 = 38-x.
2x = 38.
x = 19.

Then 5 years back of son's age it will be 14 years.

Hope you understood.

Naseem Ahmad Saifi said: (Jan 21, 2016)  
"I was as old as you are at the present at the time of your birth" means that at the time of son birth father age was equal to present son age. So father age is now double of son age. Father's age now 38 year.

If son age is x then father's age = 2x.

Given that father's age = 38.

So, 2x = 38.

=> x = 19.

5 year back is x-5.

i.e 19-5 = 14.

Kavya said: (Jan 24, 2016)  
How can we use same variable for both son's present age and father's age at the time of birth?

Sunil said: (Feb 1, 2016)  
How did we know that the father's age is now double of son's age?

As @Naseem has mentioned. How can the mere mention of a father proclaiming that "he was the same age as the present age of the son, at the time of son's birth". Indicate or point out that the father's present age is double of the son, or that the son's age is half of the father. This is the greatest unsolved mystery of this question that has been in my mind for years.

Mahendra Kumar Rudravaram said: (Feb 16, 2016)  
1. If at the time of father's age @15 years, his son was born, at that time son age is @1 year.

If father come into age @30 years, his son age is @15 years.

2. If at the time of father's age @20 years, his son was born, at that time son age is @1 year.

If father come into age @40 years, his son age is @20 years.

3. If at the time of father's age @19 years, his son was born, at that time son age is @1 year.

If father come into age @38 years, his son age is @19 years.

Finally that 19 years is present age of son.

But they are asking 5 years ago so, 19 years - 5 years = 14 years.

Azly said: (Feb 19, 2016)  
It means father's age at the time of his son's birth is equal to son's age at present.

If we take sons age at present as "x" father's age at his son's birth is also "x".

So, 2x = 38.

x = 19.

Naveen said: (Mar 27, 2016)  
How did the relation 38 - x = x arise? Explain it.

Jeetu Sharma said: (Jun 9, 2016)  
Father said "I was as old as you are at the present at the time of your birth" means that;

When son born that time age of the father is equal to the present age of his son.

The present age of his son = x.
Then father age = 2x at the current time.

So, x = 38/2 = 19.

Before 5 years = 19 - 5 = 14.

14 is the answer.

Saravanan said: (Aug 17, 2016)  
Let the son's present age be x years.

Then, (38 - x) = x -> Why 'x' is subtracted from 38?

2x = 38 -> how 2x = 38 its not mentioned in the question?

Sri said: (Sep 23, 2016)  
How 38 - x = x? Pease explain me.

Shashi said: (Nov 8, 2016)  
At present:
Age of son = x.
Age of father = 38.

At birth time of son:
Age of son = 0
Age of father = x.

As father grew son will also grow.
x - 0 = 38 - x

Think like person started at the same time and same speed but from the different location. Distance travelled by both will be same.

Usharani T said: (Dec 2, 2016)  
Can you solve the problem accurately when the father's age is an odd number?

Siva said: (Dec 29, 2016)  
Explain this 38 - x = x.

Chiranjeevi said: (Mar 20, 2017)  
@Siva.

In the question, "I was as old as you are at the present at the time of your birth"
Son's present age = Father age when son was born.

In the question father age=38, let son age be 'x'.
Father present age - son present age = father age when son was born ( i.e., son present age)
38 - x = x.
38 = 2x.
x = 19.
Sons age 5 years back x-5 = 19-5 ==>x = 14.

Dhanush said: (Jul 3, 2017)  
Son's age would always be half of father's age no matter what the father age is !

Because let say son age is 'x' now. When son born father age is also 'x'. So when son grew up and reach 'x', now father would be 2x.

So to find son age just divide fathers age by 2 (2x / 2 = x (son age) ).

Simple example: let say father age is 40.

0 x 20.
Son = <---------------->.
0 x 20 x 40.
Father= <-----------------><--------------->.

Then son ages - 5 = answer.

Karthick said: (Jul 15, 2017)  
How 2x came? Explain.

Priya said: (Jul 23, 2017)  
@ALL.

X going to other side gives x and x give 2x here.

Shano said: (Nov 26, 2017)  
How? Explain the solution.

Harini Murugan said: (Dec 31, 2017)  
let's use ratio method.

Father : Son
38 : X
X : 0

Now do cross multiplication.
i.e. 2X=38 => X=19.
Five years back, the son's age is 19-5=14.

Maha said: (Feb 14, 2018)  
How did you formed (38-x) =x?

Tej said: (Apr 18, 2018)  
Thanks to all for giving clear explanations.

Tanushree said: (Jun 5, 2018)  
Thanks for the answer.

Thakurdas said: (Jul 6, 2018)  
38-x=x? Can anyone explain this?

Yuvi said: (Jul 18, 2018)  
Please solve this.

The present age of Geetha is 5 years more than the present age of his brother Mahesh. The present age of their father is twice the sum of their ages. At the time of Mahesh's birth, his father age was 8 times of the age of Geetha.

Find their present ages.

Kira said: (Sep 23, 2018)  
@Vijay Ananad.

Nicely explain thanks.

Adhil said: (Oct 17, 2018)  
38-x=x how can it possible there for 38-15=15 40-2=2 could anyone can explain? please.

Ganesh Dadi said: (Oct 25, 2018)  
Let son age X and father age 38.
38(father age)-X (son age ) =X because father's age at the time of sons born (as per question ) =sons age i.e X.

Then 38-X = X.

Shekhawat said: (Jun 11, 2019)  
Father age is Always double of son's age so the answer is 38/2.

Post your comments here:

Name *:

Email   : (optional)

» Your comments will be displayed only after manual approval.