The ratio of Rashmi's age to her father's age is 3:5 and the ratio of her age to her son's age is 5 : 1. Four years ago these ratio were 13 : 23 & 13 : 1 respectively. The ratio of the age of the grandfather to that of the grandson 20 years from now will be?

35:13

          Father        :     Rashmi      :       son

               5          :         3

                                     5          :         1        

              25         :        15          :        3  (at present)

                                 ↓ - 2 unit

              23         :        13          :       1   (Four years before)

2 unit   = 4

1 unit  =   2

Grandfather's present age  = 25 x 2 = 50

Grandson's present age     =   3 x 2 = 6

20 years from now      F    = 50+20 = 70

                                 S    = 6  +20 = 26   

F : S = 70 : 26 = 35: 13