Multiplication factor (MF) = Selling Price ÷ Cost Price.
Case 1: Ratio 3:2
Profit = 30% ⇒ MF = 1.3.
Cost of mixture = 3 parts milk × 1 + 2 parts water × 0 = 3.
Selling price
= 3 × 1.3
= 3.9
= 39/10
So MF of mixture
= (39/10) ÷ 3 = 13/10
Case 2: Ratio 4:1
Cost price = 4 parts milk × 1 + 1 part water × 0 = 4.
Selling price (using same MF of 1.3) would have been 4 × 13/10 = 52/10.
But actual selling price remains 3.9 (same as case 1).
So, new MF
= (39/10) ÷ 4 = 39/40.
Profit/Loss % = (MF − 1) ×100
= ((39/40) − 1) ×100
= (-1/40)*100
= −2.5%
👉 Hence, Loss = 2.5%.
Long way to solve:Let cost price of milk = ₹1 per liter, cost of water = ₹0.
Case 1: Ratio 3:2
Total = 5 liters → 3 liters milk + 2 liters water.
Cost price = 3×1 + 2×0 = 3.
Profit = 30%, so Selling price = 3 × 1.3 = 3.9.
Selling price per liter = 3.9/5 = 0.78.
Case 2: Ratio 4:1
Total = 5 liters → 4 liters milk + 1 liter water.
Cost price = 4×1 + 1×0 = 4.
Selling price (unchanged per liter) = 5 × 0.78 = 3.9.
Profit/Loss = (SP − CP)/CP ×100 = (3.9 − 4)/4 ×100 = −2.5%.
So, there is a 2.5% loss.