Let  "w"  be the amount of the white sugar Dhruv bought.

Let  "b"  be the amount of the brown sugar Dhruv bought.


He used    and  .


From the problem, we have this equation

     =     ("He used an equal amount of white and brown sugar"),

or  0.4*w = 0.5*b.                         (1)


They want you calculate this ratio  

    .                       (2)


From (1), express  w =  = 1.25*b  and substitute it into (2).  You will get

    =  =  =  =  =  = .


ANSWER.  The fraction of the sugar Dhruv used was    of the total amount of the sugar.

Dhruv bought some white sugar and some brown sugar. He used an equal amount of white and brown sugar. He had 3/5 of the while sugar and 1/2 of the brown sugar left. What fraction of the sugar which Dhruv bought was used?

(1) 4/7

(2) 4/9

(3) 5/11

(4) 7/10

Let amount of white and brown bought, be W and B, respectively
As  of white (W) remained, he used  of the white (W), or 
As  of brown (B) remained, he used  of the brown (B), or 
Since the same amount of white and brown was used, then we get: 
                                                                 5B = 4W ------ Cross-multiplying 
                                                                 
Total amount used: 
 Total amount bought:  
  Fraction of total amount bought thatw's used: