In the described fertilizer, potassium compounds make up what percentage?

• A. 30%
• B. 25%
• C. 15%
• D. 20%

Answer: (C)

Percent by mass tells you what fraction of the total fertilizer’s weight is made up by potassium compounds. To find it, divide the mass of potassium compounds by the total mass of the fertilizer and multiply by 100.

If the data show, for example, that there are 15 g of potassium compounds in a 100 g sample, the calculation is 15 ÷ 100 × 100 = 15%. That’s why the potassium content is 15%.

The other percentages would require a different amount of potassium relative to the total mass. With the given data, 15% is the value that matches the portion of the fertilizer made up by potassium compounds.