How to distribute water from two 10 Litre bottles to a five and four litre bottle?

Question

There are two bottles of 10 liter; each completely filled with water. Now 2 persons having empty bottles of 4 liter and 5 liter want to take 2-2 liters of water. You can use only these 4 bottles (10 liter-full, 10 liter-full, 5 liter-empty, 4 liter-empty) to transfer the water. Wasting or throwing of water is not permitted. How can this be done?

Answer 1

1) Add into 5-L bottle 10 5 5 _
2) From 5L->4L 10 5 1 4
3) Remaining in 5L is 1 10 5 1 4
4) Put back 4L to 10-L Bottle 10 9 1 _
5) Put 1L water into 4L bottle 10 9 _ 1
6) Now add water in 5L bottle 10 4 5 1
7) Transfer 5L->4L ...now remaining water in 5L is 2 10 4 2 4
8) Current situation 10 4 2 4
9) Add 4L water into 10L bottle now 10 8 2 _
9) Add 2nd 10L water to 4L now 6 8 2 4
10) Add from 4L to another 10L water its 6 10 2 2

Answer 2

Start :- 10 10 0 0 (last two empty bottles). Step 1: 6 10 0 4 Step 2: 6 10 4 0 Step 3: 2 10 4 4
Step 4: 2 10 5 3 Step 5: 7 10 0 3 Step 6: 7 10 3 0 Step 7: 7 6 3 4
Step 8: 7 6 5 2 Step 9: 10 6 2 2 ....Achieved