Aptitude - Problems on Ages - Discussion

Aafreen Rah:

Its 3x+x because "Father's age is 3 times (3x) more than (+) his son's age (x)". Here son's age is "x" so just add "x" age to 3times (3x).

In last step why the equations are divided? Why ratio is taken?

How it is 4x?

Father's age is three times more than his son's age means. We can say (3x+x) or (3x+2x)...

Why we take it as (x+3x)?

The last step is easy but division sign gone somewhere else. Fathers age is 4X + 8 + 8 (here 8 + 8 are the years later) now divide this with sons age which is x. But after 8 + 8 years it would be x + 8 + 8 as we got x value substitute in the both numerator and denominator there you go you get as 48/24 and we taking in ratio forms as options are given in ratio like two times the son age etc.

I think answer is 2.2 times.

x = son Ronit's age now.

3x = father's age now <--- father is 3 times son.

x + 8 = Ronit's age in 8 years.

3x + 8 = father's age in 8 years.

3x + 8 = 2.5 (x + 8) <--- after 8 years, father is 2.5 times son.

3x + 8 = 2.5x + 20 <--- used distributive property.

0.5x = 12 <--- subtracted 2.5x and 8 from each side.

x = 24 <--- divided each side by 0.5.

3x = 72 <--- substituted 24, in for x, into 3x.

Son Ronit is 24 now & father is 72 now.

Son Ronit will be 32 in 8 years & father will be 80 in 8 years.

Son Ronit will be 40 after further 8 years & father will be 88 after further 8 years.

Father will be 2.2 times son after further 8 years.

2 and 1/2 == 5/2.

Since given "of Ronit's age", therefore multiply 2/5 to Ronit's age.

(4x + 8) = 2.5(x + 8).

4x + 8 = 2.5x + 20 and equation multiplied by 2.

Please explain the concept of solving this problem using shortcut method.

How can such a question be solved with in one minute?

Any other short way to solve this question?