The 3 and 5 Litre Water Puzzle

Puzzle Details : 

You have a 3 and a 5 litre water container, each container has no markings except for that which gives you it's total volume. You also have a running tap. You must use the containers and the tap in such away as to exactly measure out 4 litres of water. How is this done?

Solution :

There are two ways to solve this, maybe the question could be modified to say the 5 litre can doesn't fit under the tap...

Method 1

• Fill the 5 litre can from the tap
  
• Empty the 5 litre can into the 3 litre can - leaving 2 litres in the 5 litre can.
  
• Pour away the contents of the 3 litre can.
  
• Fill the 3 litre can with the 2 litres from the 5 litre can - leaving 2 litres in the 3 litre can.
  
• Fill the 5 litre can from the tap.
  
• Fill the remaining 1 litre space in the 3 litre can from the 5 litre can.
  Leaving 4 litres in the 5 litre can.

Method 2

• Fill the 3 litre can from the tap.
  
• Empty the contents of the 3 litre can into the 5 litre can.
  
• Fill the 3 litre can from the tap.
  
• Empty the contents of the 3 litre can into the 5 litre can. 
• Leaving the 5 litre can full and 1 litre in the 3 litre can.
  
• Pour away the contents of the 5 litre can
  
• Pour the 1 litre from the 3 litre can into the 5 litre can.
  
• Fill the 3 litre can from the tap.
  
• Empty the contents of the 3 litre can into the 5 litre can.
  Leaving 4 litres in the 5 litre can.

Watch the Video for Detailed Solution: Measure 4L Using 3 Buckets