Answers

2015-07-11T10:36:11+05:30
Hi!!!
ravi's present age = r
ravi's age 15 years later = r + 15 = 4r
so 15 = 4r - r 
     15 = 3r
15/3 = r
5 =r
so ravi's present age = 5 
ravi's present  age + 15 =20
20 = 4r 
    = 5 x 4


2 5 2
2015-07-11T10:37:56+05:30
If ravi's age (is considered 0) = 0, today
then, after 15 years from now, he would be = 15 years old
------------------------------------------------------------------------------------------------------
But, this is not so ....
consider his present age as
as per the question ,
after 15 years " his age will be 4 times his present age" 
then, let's start the equation -

ρ+15=4p

Breaking up - solution: 
then, mathematically - his age will be four ; as it is being multiplied by four. 
So, it solves the case - his age is 4, thatswhy; after 15 years, his age will 4 times 15. 

0
Sorry it is the wrong answer.
Correct ans: 5. if +15 means x4 -> +10 means x3 -> + 5 means x2 - the only age no. that will be double after 5 years is 5, see 5+5 = 10 - 5 = 5.