Q:

A milk in vendor has 21 liters of cow milk, 42 liters of toned milk and 63 liters of double toned milk. If he wanted to pack them in cans so that each can contains same liters of milk and does not want to mix any two kinds of milk in a can, then the least number of cans required is : 

• 1
  3
• 2
  6
• 3
  9
• 4
  12