Aptitude - Problems on Ages - Discussion

There are times when we take x & y both variable. So how to identify whether we have to use 1 variable or both?

For this sum answer should be option(B) which is 5/2 in fraction and in mixed fraction which is 2 1/2.

Two and half times means : 2.5.

Multiply both numerator and denominator by 2.

Thus,

2.5 x 2 / 1 x 2.

5/2 or 2.5.

And as @newbie said, if its correct then I am failing to understand that why is 3x + 8 = 2.5 x ? Shouldn't it be 3x + 8 = 2.5 (x + 8), because even the son's age should have been added to 8 right ?

Fathers age is 3 times more than his son 4x.

But after getting full stop considering and comparing other sums I can understand like this (x+8). How we put (4x+8) in fathers age?

@Poonam And @Thara in question this given that two and half.

Means 2and half which is 2.5 and 5/2 is same equal to 2.5.

Don't get confused in 2/5 and 2.5. Because 2/5 is .4 not 2.5.

2 and a half means 2*1/2 is simplified 2*2=4, and 4+1=5 is come 5/2.

Let Ronit's age = x.

Father's age = x+3x (three times more than his son Ronit) = 4x.

After 8yrs.

Ronit's age = x+8.

Father's age = 4x+8.

But father will be two and a half times of Ronit's age so.

4x+8 = 5/2 (x+8).

x = 8.

Further after 8 years.

Ronit's age = x+8+8 = x+16.

Father's age = 4x+8+8 = 4x+16.

We know the value of x is 8 so putting value of x.

Now,

Ronit's age = x+16=8+16=24.

Father's age = 4x+16 = 4*8 +16 = 32+16 = 48.

Now we will calaulate the ratio of father's to ronit's age.

Father's age/ronit's age = 48/24 = 2.

Thus 2 is answer.

@Newbie.

You made a wrong calculation 3*16 = 48 and 52+16 = 68.

Let,

Father = X.
Ronit = Y.

1st case:
X = 3Y.

2nd case:
X+8 = Y/2.

Third case:
X+16 = Y.

2X+16 = 3Y. From 1st and second case.

Then subtract third case in it. You will get,

X=2Y.