The total ages of A, B and C at present is 90 years. Ten years ago the ratio of their ages was 1 : 2 : 3. Find the present age of B.

30 years

According to question, 

    A  :   B   ;   C 

    1  :    2   :   3   ( 10 years ago ) 

Now, as per above ration, 10 years ago the age of A = X , age of B = 2x and age of C = 3x 

ATQ,

x + 10 + 2x + 10 + 3x + 10 = 90 

6x = 60 

x = 10 

present age of B = 2 × 10 + 10 = 30 years