A farmer has 1000 kg dry soil and wants each kg to contain 10 mg of phosphorus. If he applies 2 kg of a fertilizer that contains 2% phosphorus by weight, how many mg of phosphorus does the soil receive per kg of soil? Is it enough?
Answer
40 mg per kg, sufficient
The correct answer is 40 mg per kg, sufficient — Compare with required 10 mg/kg: 40 mg/kg > 10 mg/kg, so requirement is met.
Step-by-step solution
- Calculate total phosphorus in fertilizer: 2 kg × 0.02 = 0.04 kg.
- Convert 0.04 kg to mg: 0.04 kg × 1000 g/kg × 1000 mg/g = 40 000 mg.
- Divide by soil mass: 40 000 mg ÷ 1000 kg = 40 mg/kg.
- Compare with required 10 mg/kg: 40 mg/kg > 10 mg/kg, so requirement is met.
Common mistake: Not converting kg to mg or misreading percentage
Concept tested: Phosphorus requirement calculation
Published · How this solution was prepared and checked
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