Certified Arborist Practice Exam

How many pounds of Potassium are in a 50-pound bag of 20-10-5 fertilizer?

1. 2

2. 10

3. 5

4. 2.5

The correct answer is: 2.5

The correct answer is based on the percentages indicated in the fertilizer's formulation. The fertilizer labeled as 20-10-5 signifies the ratio of nitrogen, phosphorus, and potassium, respectively. In this case, the third number, 5, represents the percentage of potassium in the fertilizer. To determine the amount of potassium in a 50-pound bag, you would calculate 5% of 50 pounds. This is done by multiplying 50 by 0.05 (which is the decimal equivalent of 5%). Doing the math: 50 pounds × 0.05 = 2.5 pounds of potassium. This calculation shows that in a 50-pound bag of 20-10-5 fertilizer, there are 2.5 pounds of potassium, thus confirming that this is the correct answer.