In your hands are two 5-liter and 3-liter vats, you need to get water and get 4 liters of water from just two vases, how do you do?
Just follow the 2 steps below and get the required amount of water.
Step 1: Fill the 5-liter pot and pour it into a 3-liter pot. So in the 5 liter tank left 2 liters. Pour 2 liters through 3 liters (remember to empty all the water in the 3 liters).
Step 2: Fill the 5-liter jar then pour in until it's filled with 3 liters (now 2 liters in step 1) again, so when the 3-liter jar is full, 5 liter bottle. The remaining 5 liter bottle is 5 - 1 = 4 liters.