A company sells 10 kg of P.K.O. with 22.5 kg of Boro. What is the ratio of Boro to P.K.O. in kg per kg?

The problem states that 10 kg of P.K.O is sold with 22.5 kg of Boro.

Let $x$ be the amount of Boro corresponding to 1 kg of P.K.O.
We can write the ratio as:

To find $x$ for 1 kg of P.K.O:

Multiply both sides by 1 kg:

Therefore, for 1 kg of P.K.O, 2.25 kg of Boro is sold.

The completed table would look like this:

The amount of Boro for 1 kg of P.K.O is $\boxed{\text{2.25 kg}}$.