we are having two cann of 2lt. water and 5lt. water we have to put 4lt exactly with out measuring

Question

how to know the answer

Answer 1

Fill 2L can with water and empty into 5L can.

Repeat.

There will be 4L of water in the 5L can.

Starting with a 3L and a 5L can, how to get 4L of water into the 5L can, assuming an unlimited supply of water.

1. Fill 5L can with water.
2. From 5L can, fill 3L can from 5L can, leaving 2L in the 5L can.
3. Discard contents of 3L can.
4. Empty the 2L of water from the 5L can into the 3L can.
5. Fill the 5L can.
6. Top up the 3L can from the 5L can, leaving 4L in the 5L can.