Two buckets with a capacity of 7 and 10 liters, how can you bring 8 liters of water from the river?
We will refer to a 10-liter bucket as bucket 1, and a 7-liter bucket as bucket 2.
Fill bucket 1 and pour it into bucket 2.
Bucket 1 will contain 3 liters.
Pour bucket 2 into the river and pour 3 liters from bucket 1 into it.
Fill bucket 1 and pour it into bucket 2.
Bucket 1 will have 6 liters. Pour all the water from bucket 2 and pour 6 liters from bucket 1 into it.
Fill bucket 1 and pour it into bucket 2. Then 9 liters remain in bucket 1. Pour bucket 2 into the river and pour water from bucket 1 into it.
Bucket 1 will contain 2 liters of water. Pour water from bucket 2 and pour 2 liters from bucket 1 into it.
Fill bucket 1 and pour it into bucket 2. Bucket 1 will have 5 liters. Pour water from bucket 2 and pour 5 liters from bucket 1 into it.
Fill bucket 1 and pour it into bucket 2. Bucket 1 will contain 8 liters of water, as required.