After 2.7 liters are emptied, pour 4 liters of 1 1 liter into a 7-liter bucket.
3. Fill the bucket with 1 1 liter, fill the bucket with 7 liters of water, and leave 8 liters of water in the bucket with 1 1 liter.
4. Fill the 7-liter barrel again, with 1 1 liter barrel remaining 1 liter of water.
5. Pour 1 liter water into a 7-liter bucket, then fill it with 1 1 liter water, and then fill it with 1 1 liter water, so that1liter water will rise to 5 liters.
6. Put 5 liters of water in a 7-liter bucket, and then fill it with 1 1 liter, so there are 9 liters of water left in the bucket of1/liter.
7. Fill the 7-liter empty bucket again, and there are 2 liters of water left in the bucket of 1 1 liter.