Aptitude - Problems on Ages - Discussion

Let the present age of Rohit be 'x' years and the present age of the father be 'y' years. As per the question father is aged three times more than his son hence, y = x+3x = 4x.

Therefore present age of father is y = 4x.

Given that after 8 years, he would be two and half times of Rohit's age.

Therefore,

y+8 = 5/2(x+8).
4x+8 = 5/2(x+8) {since y = 4x}.
2(4x+8) = 5(x+8).
8x+16 = 5x+40.
8x-5x+16-40 = 0.
3x-24 = 0 => 3x = 24 => x = 24/3 = 8.
x=8,

After 8 years,

y+8 = x+8.
4x+8 = x+8 {since y = 4x}.

After further 8 years, 'k' times would be the Rohit's age.

Therefore,

4x+8+8 = k (x+8+8).
4x+16 = k (x+16).
k = (4x+16) / (x+16).
k = (4.8+16) / (8+16).
k = 48/24.
k = 2.

Therefore 2 times would he be Rohit's age.

5/2(x+8).

The ans is simple at present 2 1/2 +3=5/2 and present age is x and after 8 years +8 so (x+8).

How this 5/2 got?

Let us assume Ronit age is 10 years, Father age is 3 times of Ronit age, so 10*3 = 30 years.

After 8 years Ronit age will 18 years father age will be 2.5 times of son age, so 2.5*18 = 45 years.

After 8 years father age would be 45 + 8 = 53 years and Ronit age would be 26 years.
So, 53/26 = 2.03.
Answer is 2 times.

Very helpful to practise the problems. Thankyou all.

Why can't be father' age (x + 3)?

Why it should be taken as (x + 3x)?

Father's age is 3x + x = 4x.
After putting 4x in the equation of 4x + 8 = 5/2(x + 8), then I got 8.

Further, I found that son's age is 8 and father's age is 32 because F = 4x.
Later I made an equation F's age + 8 = Son's age + 8 * y (i.e. F + 8 = 8 + 8 * y). I can't find the solution.

Please help me out.

I have seen many solutions above but can't figure out that how they took 8 + 8 in the further 8-year equation.

Can anyone help me by explaining it?

@ Harsh

See Rohit present age comes out to be 8.

His father age is 32.

Now add 8 to both of these. Will be 16 and 40 respectively. Later is 2.5 times the former, adding 8, they will be 24 and 48 with latter is 2 times the former which is the answer. Hope it worked

How you got 5/2? I can't get that.