Asolution mass of 1 kg is times greater than 100 g, thus one kilogram (1 kg) of a 2.5% ki solution would contain of ki.

The answer is "A solution mass of 1 kg is 10 times greater than 100 g, thus one kilogram (1 kg) of a 2.5% KI solution would contain 25 grams of KI."
A 2.5% by mass KI solution is equivalent to 2.5 grams of KI divided by 100 grams of the KI solution and then multiply by 100. We can multiply 10 to the masses of the solute and the solution so that 100 grams becomes 1000 grams.      
     2.5% by mass = (mass of solute / mass of solution) *100
                             = [(2.5g*10) / (100g*10)] *100
                             = (25g solute/1000g solution) *100
Since 1000 grams is equal to 1 kg, the expression becomes
     2.5% by mass = (25g solute/1kg solution) *100
Therefore, 2.5% by mass KI solution would contain 25 grams KI in 1 kilogram solution.

It changes food into energy that the organism can use.