The Solutions

At the Farm

Kayla from Nova Scotia Canada, Age: 13
Fill the 3 liter and pour it into the 5 liter. Fill the 3 liter again, pour what you can into the 5 liter and you'll be left with 1 liter in the 3 liter container. (3+3=6 6-5=1).
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Matt Rules from CT, Age: 10
First, you fill up the 3 liter container and pour it into the 5 liter. Fill up the 3 liter again and pour in 2 liters in the 5 liter because that's how much can fit. Bingo, now you have one liter..
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Ruve from Delaware, Age: ?
Take the 3 liter container and fill it. Pour it into the 5 liter container. Then refill the 3 liter container and pour it into the 5 liter container. The overflow is 1 liter. Point to the tabletop and say, "The milk that spilled over is yours.".
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nicole from england, Age: 6
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Aly from France, Age:
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michael from hawaii, Age: 6
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aditya from sharjah U.A.E, Age: 9
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ashes from usa, Age: 12
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The fabulous me from US, Age: 11
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Jameka Horton from Columbia S.C, Age: 11
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Some answers dealt with more practical approach:

rosco from north carolina
get the customer to bring in a one liter container to pour the milk into or take the 3 liter container and mark three equal sections repersenting the 3 liters..

Samantha from Ohio
only fill the 3-liter container 1/3 to equal 1-liter.

Caitlin from California United States
Julia is going to take the 3-liter and devide it evenly in thirds. She will sell 1/3 to the customer..

Marissa from Massachusetts
Julia can use the 3-liter container. She can divide the volume of the container by 3 and fill only that much up. That would equal 1-liter.

Julia from Florida
Sell them the 3 liter for the price of 1 liter or tell them you just don't sell 1 liter containers and your sorry..

Tiffany Lauren Santi from Florida
first you have to fill the five liter with milk.then you have to pour as much as you can in the three liter.then throw out the three liter.pour milk from the five liter to the three liter until they look the same..

me from here
poor milk in a measuring cup, then put it in a one liter bottle.

Danielle from Mississippi United States
Use a measuring cup to measure 1 liter..

Doris Teo Ming Jiao from Singapore
she's going to measure in the 3liter container because the container is 2 more parts than 1liter. When the customer wants 1liter of milk she can easily see how mch the cutomer wants by looking and pouring into the container..

nicey cooly from Colorado
Divide the 3 litre container by 3 and you get 1 litre, and you divide the 5 litre container by 5 and you get 1 litre..

charlis from tx
1. fill the five liteer container 2. fill the 3 liter from the five liter container 3. divide into half the remaining 2 liters in five liter container.

sarabear from usa
with a measureing cup!.

sapphire from mississippi
pour the milk until it reaches the next line.

baby cake from Mississippi U.S.A
By taking 4 liters away from the 5 liters contrainer or by taking away 2 liters away from the 3 liter contrainer..

Maybe some of you will figure out how this answer relates to our milk problem:

Nancy from California
My friend Marcela is acting like a witch. Me and my friend's all think she's a witch..