Four bottles and water puzzle

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?

Note: It is assumed that you can not measure water level by comparing water level, or by judging, it should be exact 2 liters of water finally in each 4 and 5 liter water bottle.

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Labaratory rat

There are 8 idential containers filled with same material from which one has some poison added to it. Scientists can run find out it a container is poisonous by giving some of the liquid to a laboratory rat. The result would be revealed after a week. They only have one week to find which one is poisonous. The question is what’s the minimum number of laboratory rats they can use to find the poisonous container?

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Three oily rope puzzle

We have three ropes of the same length and all burn in 1 hour if inflamed from one side. The have oil at random parts. This means they don’t have consistent rate of burning throughout the length.
Rule: you can only burn from the sides of the rope and not anywhere alongside the length.
How can we get 1 hour and 15 min from burning the ropes?
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