Logical question with a balance and flour The problem is: I have a balance of $9$ kgs of flour and two weights; $250$g and $50$g. In the matter of $3$ steps I have to divide them into $2$ bags of $7$ and $2$ kg, respectively. I know that after I have measured a bag with $250$g I can combine it with the $250$ weight, so $500$g in total for example. Using the balance counts as a step! So you can use the balance only 3 times.
I hope you understand my English :]
The problem is really to measure out $2$ kg of flour in one bag.
The second bag simply receives all the remaining flour.

If you are allowed to put two bags on the scale and then transfer flour
between them until the scale balances, you can use the scale to
divide a bag of flour in half in one step.
Put the bag to be divided on one side of the scale,
put an empty bag on the other side, 
and transfer flour between the bags until they balance.

Assuming you can divide a bag as described above,
here is a hint about how to measure $2$ kg 
from the original $9$ kg in three steps:
$$ 9 = 2.25 \times 4. $$
I'm not sure if I am allowed to answer on my question but I solve it.
First I combine the 250 and 50g weight and I got a bag of 300g.
Then I combine the bag of 300g and the weights of 250g and 50g - I get a bag of 600g. Then lastly I combine the 600g and 300g bag the 250 weight and put the 50g weight on the other side of the balance. I got a bag with 1100g. 
1100g + 600g + 300g = 2000g = 2kg.