Question

if a half litres milk cost 22 rs. what 7 litre cost

Answer 1

Half l=₹22
1 litre=₹44
7litre=₹308

Answer 2

Half liters of milk = 500 milliliter 
500 mm = Rs.22
7 litres = 7000mm
(7000/500)*22 = Rs. 308