How much water must be added to a bucket which contains 40 liters of milk at the cost price of Rs.3.50 per liter so that the cost of milk reduces to Rs.2 per liter?

A. 25 liters
B. 28 litres
C. 30 liters
D. 35 liters

Explanation:

Total cost price =Rs(40 x 7/2) = Rs.140

Cost per litre =Rs.2,
Total quantity = 140/2 = 70 Litres.
Water to be added =(70-40) =30 Litres.