If x ml pure alcohol is added to 400 ml of a 15% solution and after adding its strength becomes 32%, then the value of x is
(a) 50 ml (b) 75 ml
(c) 200 ml (d) 100 ml

We calculate as  follows:

15 mL pure ethanol / 100 mL solution (400 mL) = 60 mL pure ethanol

32% = 32 mL pure ethanol/100 mL solution = 60 mL pure ethanol + x mL pure ethanol / (400 + x)

x = 100 mL pure ethanol was added to the solution > OPTION D