Question 267284
Given, 40 kgs of a solution contains 10% of salt.
So, the quantity of salt in the solution = 40*(10/100)=4 kgs
Let x kgs of water be evaporated so that the new solution contains 25% salt
    (40-x)*(25/100) = 4
    (40-x)*(1/4) = 4
     40-x = 16
       -x = 16-40
       -x = -24
        x = 24 kgs